Sir Tim, who was knighted in Mrs Thatcher's resignation honours and helped her win two election campaigns, is advising Mr Birt on how best to quell the uproar that has arisen since the Independent on Sunday first revealed two weeks ago that the BBC chief was paid through a private company.
Sir Tim's services are believed to include persuading the BBC Governors not to answer press questions; indicating to journalists that he would try to give them access to Mr Birt on condition that their papers did not publish editorials calling for him to quit; counselling Mr Birt's allies on what they should say to the press, and fostering the notion that Mr Birt is now the victim of a concerted campaign and the target of criticism which goes far beyond his financial affairs.
Lowe Bell Communications, Sir Tim's media consultancy company, has been retained by the BBC for the last five years to advise on corporate communications. This has embraced the corporation's advertising campaign, brochures and 'on air' interviews with senior BBC executives. The BBC has its own press and public affairs department. But in the last few days, Sir Tim has taken on a more prominent role. The job he is doing for Mr Birt is similar to the one he did for David Mellor, the former Heritage Secretary, during the Antonia de Sancha revelations and the one he is still doing for British Airways in the aftermath of the Virgin 'dirty tricks' affair.
Yesterday, Mr Mellor was widely quoted defending Mr Birt and calling for an end to the 'witch-hunt'.
'Mr Birt should not be driven out of office because of his accountancy arrangements,' Mr Mellor said. 'It is in danger of becoming a national disease - once we have got something on someone, everyone else leaps in for the thrill of the chase. It would be a great loss to the BBC at a crucial time in its history if John Birt had to leave.'
While Mr Birt has hitherto refused to give a detailed interiew about the row, sources close to him are privately accusing 'a disaffected mob' of senior broadcasting figures, including Alasdair Milne, the former BBC director- general, and Ian McIntyre, the ex- head of Radio 3, of trying to unseat him.
The sources have also been raising the issue of what would happen to the BBC if Mr Birt resigned, and trying to cast doubts on the abilities of John Tusa, formerly managing director of the BBC World Service, who is a possible successor.
Their aim has been to keep Mr Birt in place until the crucial BBC governors' meeting on Thursday. Anonymous quotes from BBC Governors that have been critical of Mr Birt have been dismissed as journalistic invention by his supporters.
Robert MacLennan, the Liberal Democrat Home Affairs spokesman, yesterday told Peter Brooke, the National Heritage Secretary, that the BBC chairman should take prime responsibility for the Birt affair. He said Marmaduke Hussey had shown 'consistently poor judgement in handling changes at the top'.