When Benjamin Zephaniah was a boy, he wrote Bob Marley a letter - and got a reply. He has worshipped the reggae superstar ever since. But as six more 'unreleased' tracks adorn yet another 'best of', he says it's time to leave brother Bob alone

Bob Marley was great, but we all know that. Even if you don't like reggae, you can't ignore the fact that his music had an uplifting effect upon the music-loving world. I don't think I've ever visited a country where he is not known - and that can't be said of Cliff Richard.

Liberals use Marley as a password, and I've lost count of the number of times people have said to me: "I don't know much about reggae music but I like Bob Marley." Some Rastafarians see him as a modern-day prophet; there is a band in New Zealand who have dedicated themselves to doing Marley cover versions; there is a tribe in South America that worships him. My mum loves him, and so do I.

Not only do I think he was one of the greatest musicians to appear on planet earth, I think he was a really nice bloke. When I was just a kid, a struggling unknown poet ranting on the streets of Birmingham, he was the only singer who ever replied to any of my letters. I actually got advice from brother Bob: he told me to "keep it up", to "stay militant", and he said that one day people would read my poems. It's impossible to say exactly how much that meant to teenaged me. Bob Marley was my hero, and then he became my penpal. Very heaven.

I grew up to the sound of Marley. I was listening to him when the band were simply known as the Wailers, before they were "repackaged" with Marley as the frontman. Trust me - back then I was their biggest fan. Throughout the history of the Wailers, and Bob Marley and the Wailers, they never released a dud album; every one was a classic. But since Bob Marley's death in 1981, there has been a string of posthumous albums, and every one them, with the possible exception of Confrontation, has been floored.

Bob Marley can't be blamed for this, and neither can the Wailers: most of the surviving members of the band are involved in court actions claiming that they have been ripped off in one way or another. And I feel like going to court, because I feel like I'm being ripped off, too.

I've got all the real Wailers and Marley and the Wailers albums, but I also have LPs such as King of Reggae, Lively Up Yourself, Songs of Freedom, Dreams of Freedom, Chant Down Babylon, Soul Almighty, Soul Captives, Legend, and many more. They sell them at car boot sales, petrol stations, post offices and newsagents. I even have two albums called Natural Mystic and they only have one track in common: a track called Natural Mystic.

What all these albums do have in common is they are all so-called Best Of albums, or they claim to contain "rare" tracks that are "newly discovered" or "digitally remastered remixes". The truth is that Marley put out the best of his tunes when he was alive, and what we now have is various record companies trying to make as much money as they can from the icon.

Universal Music has recently acquired the rights to 211 Marley recordings, and to celebrate the completion of the deal they have just released a three-CD box set called Grooving Kingston 12. They say, to their credit, that unlike other "backstreet record labels" they will pay the musicians their royalties, and they also claim that they have six previously unreleased tracks. Two of them, Music Gonna Teach and One Love True Love, appear on the first new box set.

I've listened to all six tracks, and they are certainly not the best of the Wailers. Actually, they're not very good.

I don't believe I just wrote that. How could I? I'm his biggest fan. But did I say that there are some Bob Marley tunes that are not very good? Is that allowed? Have I blasphemed? There is a kind of political correctness, a politeness, that dictates that you can't say a bad thing about Bob Marley tunes, and now I risk being force-fed meat by angry Rastafarians. Hippies will curse my karma, and my mum will slap me when she reads this. But it's true - if these tunes were hot, they would have been released years ago.

At the beginning of the 1990s I remember being in the Fallout Shelter, a recording studio owned by Island Records, when someone came in rejoicing and proclaiming that a brilliant Marley recording had been discovered. I was in the middle of recording another one of my obscure political albums; it was going well, but I had to stop. I had to sacrifice my precious studio time so that my producer could use the studio to quickly release this new old tune. But I didn't complain; there was something surreal about being interrupted by Bob Marley.

What happened next was like an emergency surgical operation. The studio was blocked off and only those with the password could enter. Top musicians were brought in; they swore an official secrets act and began to record overdubs and add more horns, and then the track was given the best treatment money could buy via a state-of-the-art digital mixing console. That track was called Iron Lion Zion, which went on to become a big hit worldwide.

Now that's what happens when a genuine gem is found. Why would a record company place a newly discovered work of art on an album that's a collection of oldies and call it a bonus track? If it was good enough they would release it as a single in its own right, even if it needed attention from fresh musicians in north London.

I'm just a keen Bob Marley fan who feels exploited. All of these posthumous releases have nothing new to offer - how many times can you listen to a slightly different mix of that tune recorded in 1968? How many more tapes are waiting to be found in the vaults of recording studios in deepest, darkest Jamaica? At the height of his career Bob Marley could have had the Red Sea parted if he requested it, so have no doubt about it - if he had wanted a track to be released, it would have been released.

The new tracks on this new release are not terrible, but they're not great. As on many of the early recordings, Marley is trying stuff out, experimenting and tuning his writing and recording skills. When you listen to his early works you find that there are many versions of the same songs; many songs borrow lines from each other, and many recordings are drafts of the greater things to come.

On the track called Black Progress, it sounds as if Marley is trying to come up with a black power anthem in the style of James Brown's Say It Loud, I'm Black and I'm Proud. Marley tries to rouse us with a rather overdone American accent, which he was never to try again, and we know why.

What I found most painful, listening to this new box set, is the acoustic tracks on the third CD. You could say this is all good, that Bob Marley Unplugged is another good angle and capturing the reggae master sitting around a fire playing his guitar could be very cool - but I suspect something more sinister. These recordings are so unfinessed, they sound like the CIA have been eavesdropping on a rehearsal.

I may be wrong - one of these recordings could make the charts and a whole new genre of music could be created. It could be called reality music: yes fans, listen to the puffing, the arguments, the conversations, and vote for your favourite musician. On Stir It Up you even hear Bob asking the backing singers if they are in tune ("You have dat?"), and all you get for your money on Guava Jelly is one chorus lasting 43 seconds.

I didn't find this painful because of Bob's performances - after all, there are only a few times when you can hear him sing so intimately without the trappings of the band. I just felt that I hadn't been given permission by him to hear all this. I don't believe that he would want all of these recordings in the public domain. Quite honestly, I felt as if I was colluding with the record company in a grave-robbing venture.

Bob Marley was always at the cutting edge of what is sometimes called roots music. One of the great things about him was the way he managed to keep the essence of reggae in his work while at the same time making sure that every new album was a true step forward; no two albums sounded the same.

I recall a music journalist asking him what he thought of the Two Tone ska revival. Marley laughed and went on to explain that he just couldn't see why anyone would want to go backwards after all the years of hard struggle that people like him had endured to move the music forward.

It would be a much greater tribute to the memory of Marley if those record companies that have make so much money from the Wailers began to invest in some of the reggae artists of the future. But that may be asking too much.

Most record companies exist not because they love music but because they love money, and Bob Marley has made more money in death than he ever made in life. Marley has become a brand.

His old house in Kingston, Jamaica has become a museum, and I have heard his music being played in places where Rastafarians are not even allowed. Fair enough, the hungry must be fed, but even here in Britain his music has been used to sell soap and mortgages. Not only will the revolution be televised, it will be advertised.

If you are the kind of fan who wants a recording of every single word that Bob Marley ever said, if you want to know everything he ate, drank, touched and smoked, if you really think that you will not be a complete person unless you capture every breath he took, then feel free to go on spending your hard-earned cash - the record companies will not complain. But remember what Marley said: "It's only a machine that makes money."

If you are the kind of fan who respects the artist, however, just love what he has given to you. And if you feel the need to play a part in keeping his name and legacy alive, buy real Wailers goodies, or help the poor of Jamaica by sending financial donations to the Bob Marley Foundation. Even if no more Marley tunes are ever found, he will still live forever.