He has always enjoyed a reputation as a controversial figure. But last night an extraordinary story about how BBC director general Mark Thompson bit a newsroom colleague was sweeping the corridors of the corporation.

The bizarre, apparently unprovoked, attack was on senior television journalist Anthony Massey. Thompson's 44-year-old victim suffered clear bite marks through his shirt, and immediately reported the incident.

Their bosses were so determined to hush up the affair, however, that Massey was promptly sent to Rwanda on a perilous assignment. And Thompson, then a rising star, was allowed to continue his soaring career unhindered.

The story has only become public thanks to a leaked e- mail exchange between Newsnight presenter Jeremy Paxman and Massey, in which Paxman observes that the director general 'is quite clearly insane'.

A spokesman for Thompson last night confirmed the story, but claimed it was 'horseplay'.

The tale began to make its way into the public domain when Paxman emailed Massey, who is now on the BBC's foreign news desk but long worked in Bosnia and elsewhere as Kate Adie's producer.

Paxman asked: 'I've got to interview Mark Thompson tomorrow. Is it true that he once bit you?'

Massey replied too late for the big interview, but gave full detail. 'It is absolutely true,' he said. 'It was 1988, when he was the newly-appointed editor of the Nine O'Clock News, and I was a home news organiser.

'It was 9.15 in the morning. I went up to his desk to talk about some story.

I was standing next to him on his right, and he was sitting reading his horoscope in the Daily Star (I always remember that detail).

'Before I could say a word he suddenly turned, snarled, and sank his teeth into my left upper arm (leaving marks through the shirt, but not drawing blood). It hurt.

'I pulled my arm out of his jaws, like a stick out of the jaws of a labrador. The key thing is, we didn't have a row first, or even speak, and I had never had any dispute with him.

'He was recently arrived in the newsroom, and I hardly knew him. He just bit me in the arm for no reason without any warning or preamble.

'I don't think it was personal. Something turned in his brain, and anyone who had been standing there at that moment would have been bitten, Linda from the teabar, the BBC chairman, Keith Graves, anyone. It just happened to be me.

'Thompson didn't apologise or explain, so I went to complain to my then boss, Chris Cramer. All Cramer said was, "This whole place is full of f****** headbangers", which was a fair point and indeed is still true, but didn't help somehow.

'I wanted to bring the whole BBC disciplinary process down on Thompson's head, but Cramer was desperate for that not to happen.

So I got sent abroad on some story for a month or so, and when I came back it had lost momentum, and I never pursued it.'

Massey added that 'in those days it seemed quite acceptable for senior people to bite junior colleagues'.

He said he and Thompson had met a number of times since, 'but in a very British way, neither of us has ever mentioned it. I last saw Thompson just after he was made DG, at the BBC News 50th anniversary party in May.

'He saw me across the room and went white. I don't know why. I don't bite.'

Massey added he had been told Thompson once tried to throttle a video editor for completing an obituary of a famous actor too late for broadcast.

Paxman replied: 'The bloke is quite clearly insane. Bloody hell. If any of this came out, he'd be toast.'

The BBC said: 'Mark did bite him but it wasn't intended to hurt him. He thought he was doing something funny.

'When he was later told that Anthony thought he had "gone for him", Mark went up and said sorry and tried to make amends.

Mark does remember the incident because he remembers Anthony took it the wrong way. It was horseplay.'

Officials said no action would be taken against Paxman or Massey over the leaking of the e-mails - and denied Thompson read Daily Star horoscopes.

Privately BBC officials denied Thompson had attempted to strangle a colleague.

Thompson, 47, joined the BBC from Oxford. He rose to controller of BBC2 before joining Channel 4 and becoming chief executive. He was wooed back to the BBC as director general last May.

A BBC source said: 'Massey is quite aggressive himself and has had dust-ups with a number of people.

He recently swore at the editor of the 1pm news in the middle of the newsroom.

'Everyone says him and Kate Adie are the only people mad enough to work with each other.'