Mr Mates has told close colleagues that he believes the pursuit of Nadir arose because his economic success in Northern Cyprus was blocking an international settlement between Turks and Greeks which would have unified the divided island.
The extraordinary claims, mirroring those made by Nadir himself, lie behind the representations which Mr Mates made not only to Sir Nicholas Lyell, the Attorney-General, but to his predecessor, Sir Patrick Mayhew - now Mr Mates's boss at the Northern Ireland Office.
Even if Mr Mates's claims about MI6 were proved to be true, they will place his ministerial career in jeopardy. They put a minister responsible for day-to- day security service activity in Northern Ireland at odds with a key intelligence agency.
According to one source who has talked about the case to Mr Mates within the last month, the minister insists that he believes passionately in Nadir's innocence. He also says that the intelligence services 'wanted Nadir out of the way because he was an obstacle to an American-backed plan to unify the island'.
The source said, however, that he believed Mr Mates had ceased to argue Nadir's case to the law officers after the tycoon jumped his pounds 3.5m bail last month and fled to Northern Cyprus. Later, the Prime Minister rebuked Mr Mates for his 'unwise' gift to Nadir of an inscribed wristwatch.
Neverthless Mr Mates, aware of the growing vulnerability of his position, will come under pressure to substantiate claims about MI6's role. He is understood to have made them explicit in written representations to the law officers.
Last night Mr Mates said: 'I have not commented on this affair since it started - and I am not going to start now.'
If the revelations force Mr Mates out of office, the Government knows he would not go quietly, and would be likely to make an explosive personal statement in the House of Commons detailing some of the questions raised in his submission to Sir Nicholas. The persistence of Mr Mates's defence of Nadir has persuaded MPs that the Northern Ireland minister - who has never shied away from parliamentary controversy - is convinced of the case he has made, and has evidence to back his argument.
Labour demanded Mr Mates's resignation yesterday for accepting the loan of a car from one of Nadir's public relations consultants. And new evidence emerged that the Tories solicited funds from the fugitive businessman.
Brendan Bruce, the Tory director of communications from spring 1989 to December 1990, has said that he approached Nadir to 'extract' money from him for party funds. The Conservatives have so far suggested that donations received from Nadir were not solicited by them. John Major told the Commons last week: 'Donations to the Conservative party are freely offered and they are accepted on that basis.'
But in his book Images of Power, published last year by Kogan Page, Mr Bruce wrote: 'A few years ago I was lunching with the industrialist Asil Nadir in a (vain) attempt to extract money from him for Tory party funds. Naturally enough, I was trying to convince him that we needed more money for the party's marketing programme.'
The last of Nadir's donations, which he claims amount to pounds 1.5m, was made in March 1990. It is not known if the lunch occurred before or after the Serious Fraud Office began its investigation into Polly Peck in August 1990.
But there were signs that senior ministers are becoming more anxious about the rows engulfing Tory financing. Government business managers are to allow a debate soon on recommendations by the Select Committee on Members' Interests, which would force MPs to name any clients with which they have connections - rather than simply stating the name of the PR or lobbying firm by which they are retained. Yesterday the Independent revealed that Gerry Malone, Tory party deputy chairman, had worked as a consultant for Nadir's publicity advisers Morgan Rogerson until three weeks after Nadir fled the country. Mr Malone recorded this relationship in the Register of Members' Interests. But he has denied ever meeting or acting for Mr Nadir.
Tory embarrassment over links with Nadir has intensified with the Independent's disclosure that Mr Mates accepted the loan of a car from Mark Rogerson of Morgan Rogerson. The car, a second- hand Volvo 240, was purchased last month after Nadir's flight to Turkish Cyprus.
Mr Mates's decision to accept the loan prompted Frank Dobson, a Labour frontbencher to say: 'Mr Mates should go. He shouldn't get a car from an organisation which is promoting the interests of a fugitive from justice.'
Mr Mates found the Volvo himself in a dealership in Sheet, Hampshire, and recommended that Mr Rogerson, who he said was looking for a new car, buy it. It was bought on a hire purchase arrangement in Morgan Rogerson's name, and lent to Mr Mates's estranged wife and former secretary, Rosellen. Friends of the Mates's said that she asked for a car to tow her horsebox.
Mr Mates insists the car was returned after 10 days, he says. He denied impropriety.
Inside Story, page 17
Leading article, page 22