Mr Gould said that the free 1989-90 holidays enjoyed by Mr Mellor and his family - in the Persian Gulf, as the guest of Sheikh Zayed, ruler of Abu Dhabi; and Marbella, as the guest of Mona Bauwens - were worth at least pounds 10,000.
Yet the ministerial guidance on such matters, Questions of Procedure for Ministers, states that when gifts cannot be refused 'without the risk of apparent discourtesy', then 'certain rules apply'. Those rules say: 'Gifts of small value (currently this should be put at up to pounds 125) may be retained by the recipient.
'Gifts of a higher value should be handed over to the department for disposal, except that (i) the recipient may purchase the gift at its cash value (abated by pounds 125); (ii) If the recipient wishes to reciprocate with, and pay for, a gift of equivalent value, the gift may be retained . . . '
Mr Gould said last night: 'These rules were established to protect standards of conduct in public life and David Mellor's lack of concern for these rules creates a picture of a minister who was prepared to use ministerial power for his own personal pleasure.' He said that pounds 10,000 was 'a fairly conservative estimate' of what the two holidays would have cost, and added: 'He's got to account to somebody, in this case the Treasury, for the gifts he has received.'
But in a letter to Mr Gould last night, John Major endorsed Mr Mellor's decision not to refer to the then prime minister, Margaret Thatcher, his family holiday in 1990 paid for by Mrs Bauwens.
'The guidance says that a minister should not accept gifts or hospitality which would, or might appear to, put him or her under an obligation,' Mr Major wrote.
'It makes clear that this is primarily a matter which is left to the discretion of ministers, although in cases of doubt or difficulty ministers are encouraged to consult the prime minister. So it is not the case that ministers are required to report all gifts or hospitality to the prime minister.'