Byline: MATT BORN

SUSPICIONS of a new Labour smear campaign against broadcaster John Humphrys hardened last night.

It emerged that Alastair Campbell's former right-hand man Tim Allan may have been behind damaging claims that the Today presenter launched a four-letter tirade against ministers.

Mr Allan, who spent four years as Mr Campbell's Downing Street deputy, was sent the only videotape of the veteran broadcaster's controversial after-dinner speech last week.

By the next day, the tape had been leaked to the Labour-supporting Times which devoted two pages of its Saturday edition to allegations that Humphrys had 'ridiculed senior Labour politicians and implied that all ministers are liars'.

The story - which appeared to cast doubt on the impartiality of the BBC's most high-profile political interviewer - was potentially hugely embarrassing to both Humphrys and the BBC.

But with the finger of suspicion now pointing at Mr Allan, the revelations are likely to backfire on Downing Street and inflame tensions between Number 10 and the BBC. The controversy erupted after The Times published extracts from a speech Humphrys gave to the Communication Directors' Forum on June 8.

The paper said he launched a foulmouthed tirade against ministers, including Tony Blair, Gordon Brown and Peter Mandelson, and also insisted that the Today programme had 'got it right' over Andrew Gilligan's story that Number 10 had 'sexed up' its dossier about Saddam Hussein's weapons of mass destruction.

Last night, the head of the company that organised the conference said Mr Allan had been sent the only videotape of the speech. Mark Rayner, chief executive of Richmond Events, said: 'Tim Allan contacted us last Thursday because he had seen a copy of our newsletter, which included a picture of John Humphrys and a quote from his speech.

'Mr Allan wanted to check that the quote was accurate so we sent him the tape in a bid to reassure him that it was. …