When Ali Campbell announced his departure from UB40 in January, war broke out inside one of Britain’s most successful musical families.

Ali, his brother Robin and six school friends founded the group in 1979 and went on to become the best-selling reggae band of all time.

UB40 moved swiftly to replace Ali, their singer, with his elder brother Duncan, and with separate tours planned by Ali and by the band, a battle is raging.

In a bitter war of words the band accused Ali of becoming money hungry, of being manipulated by a Yoko Ono-like second wife, and of wanting to sack management after 30 years loyal service.

He had, they said, suffered a mid-life fashion crisis.

Big brother Robin doesn’t beat about the bush. “It’s like a divorce,” he says, “and we are currently fighting for custody of the songs.”

Ali, on the other hand, insists he left because of a dispute with the managers behind UB40 and is fighting a legal battle to get hold of his former band’s accounts.

“This all seems to be a very sad and desperate attempt to discredit me and manipulate the fans,” he says – through his new management…

But both sides do at least agree on onething – that all this squabbling has become just a bit Spinal Tap.

In their first interview since the split, the rest of the Birmingham based band’s anger and sense of betrayal towards their former singer is unmistakable.

Robin says: “Ali moved down south, got married again and got new management.

He was constantly being told that he should be earning more money by people that don’t know.

The band’s always been a democracy and that became a bone of contention for Ali. He demanded not just that we sack the management but everybody who works for us.

“Ali is calling his tour The Best of UB40 – 1980-2008. That disgusts me, the people who made the songs are here in this room.”

There is plenty at stake. UB40 are one of the most successful British bands.

They topped the charts on both sides of the Atlantic in 1983, with Red, Red Wine, and in 1979 were the first reggae group to play in Moscow.

And 18 years later they were a big enough draw to play the Cape Town leg of Live 8.

The rift between singer and band initially stemmed from a row over Ali’s solo album Running Free which the band claims he insisted on finishing ahead of the new UB40 album.

And by the time the album was completed in November 2007 Ali had made it clear that unless the band’s financial team was sacked and entire organisation restructured, he would quit.

“It was heartbreaking,” says sax player Brian Travers.

“We can’t make people unemployed, there are people who have worked for us for 25 years and couldn’t work for anyone else. We had a tour in Australia – 20,000 people a night planned and Ali said, ‘I’m not going’.

“The promoter said, ‘Yes you f***ing are or I’ll sue you’.

So he did it, but under a terrible cloud. He didn’t talk to us, and used to walk off stage, get in a car and go to his own hotel.”

Drummer Jimmy Brown was enraged when Ali’s new management told him to treat their charge ‘with more respect.

“I’d worked with him for 30 years, so it was like, ‘Who do you think you are?’ “It had all got a bit like Spinal Tap …his new wife would suggest how we should do things. We finally knew there was a bit of a mid-life crisis when he started dressing like Elvis with his collars up.”

In the end, Ali’s brother stepped into the lead singer’s role – much to Ali’s chagrin.

While his younger brothers were making millions around the world with UB40, spending an astonishing 214 weeks in the UK singles chart in the 1980s, Duncan had spent the years as a croupier, running nightclubs, managing bars and a snooker hall.

“I haven’t JUST spent 30 years crying because I refused to join the group when it started,” he laughs.

“Ali actually phoned at the same time Robin had come round to my flat to talk about the situation.

“Ali was saying they’d all let him down and it had all gone wrong and how I was his last friend and would I go to Australia with him as he had no mates.

“I said I’d got this job coming up – and we haven’t spoken since.”

With a new album and full diary of international dates ahead, UB40 are determined to show that their pulling power without their former frontman hasn’t diminished.

They have a score to settle. Jimmy says: “I think Ali just wanted us to go to sleep for a year so that he and his management could clean up.”

Robin adds: “He wanted us to fall apart and disappear so that our fans would go to his shows. When we said we were touring without him, I think he was shocked.

When our fans stuck with us, I think that was the biggest kick in the balls for him.”

Brian says with a laugh: “Celebrity Big brother beckons for Ali. We took 30 years to build up what we’ve got, it didn’t just happen over night.

“UB40 is known everywhere – Ali Campbell isn’t.”

Brian hopes that one day his friendship with Ali will be mended – but not yet.

Jimmy explains: “The wounds are still too raw – Ali tried to shaft us basically.”

Ali – who lives in Bournemouth with Julie and their four children – sounds exasperated.

In a statement through his management, he says: “This is all getting a bit Spinal Tap and seems to be a very sad and desperate attempt to discredit me and manipulate the fans. However, as I have said repeatedly, there is an ongoing legal investigation which is coming to fruition and which will speak far more eloquently than I could, or indeed would want to, regarding bringing the truth and the facts to light.”