Downing Street, as a matter of routine, refused to discuss the conditions as it emerged that the advisory committee on ex-permanent secretaries' appointments had reservations about the move.
At least one member wanted to bar Sir Duncan from taking up the post for 12 months and two conditions were imposed. One was that Sir Duncan should not join Bupa's board until 1 October, six months after he left the NHS. The second, Sir Duncan said, was that 'I would not be personally involved in any dealings with the NHS Executive for a further 18 months.'
Sir Duncan, 53, defended his involvement with Bupa - thought to be worth pounds 15,000 a year - on the grounds that his interests lay with its pounds 232m hospital business and Bupa's development of 'managed care' - ensuring money is spent only on proven treatments.
But he said that as a board member he would back the provident association's policy of seeking to extend tax relief to all private medical insurance. He saw no conflict between that and his role until five months ago as chief executive to the NHS.
'It would be surprising to me if the vast majority of health spending did not continue to come from general taxation,' he said. Given that the shift between public and private spending was likely to be at the margins, he added: 'I don't think it would be significant enough to make it difficult for me'.
But David Blunkett, Labour's health spokesman, found Sir Duncan's position 'incredible'. 'It is impossible to see how seeking to extend tax relief on private medical insurance can be compatible with support for the NHS.' The hospital side accounted for only one-fifth of Bupa's income, Mr Blunkett said. 'Its core business is to sell more private health insurance and it does so in part by running down the services that the NHS provides.'
Labour's attack came as Sir Duncan said the idea of a gulf between public and private health care was 'old hat'. If the NHS bought more services from the private sector, 'it is those who buy the services who control the principles of equity and of equal access for equal need'. The NHS would stipulate the quality and value for money, so buying care from the private sector 'does not in any sense undermine the NHS'.
Mr Blunkett argued that the conditions imposed on Sir Duncan were 'plainly inadequate. It does not prevent Sir Duncan using his considerable contacts with NHS trusts and health authorities, along with the other knowledge he brings with him. In an increasingly market-orientated health service, Bupa is clearly now a direct competitor for the NHS.
'This Conservative government is destroying the fine tradition of public servants acting in the public interest which has served this country so well for so long.'
Sir Duncan also fiercely denied that his involvement with Bupa would invalidate the work of Health 2000, an independent study of the future of the NHS which, among other things, will examine the way it is funded. Members of the committee brought various views with them, but would have no truck with any member who advanced the view of any sectional interest, he said.
Tom Sackville, the junior health minister, said Sir Duncan was 'perfectly free' to join Bupa. 'The private sector is not harmful to the NHS. It complements it. We use them as a very useful form of comparison and competition with us,' he said.
Leading article, page 12