The Euro-sceptic Mr Murdoch made clear that it was the question of the single currency which would dictate who he supported.
And he implied that his best-selling newspaper, the Sun, would back the Tories if the premier came out against the European single currency.
When Mr Major refused to change his policy of "negotiate and decide", the Sun went over to Labour in what was considered a vital boost for Tony Blair.
Details of the pressure Mr Murdoch brought to bear were revealed last night by Sheila Gunn, who was Mr Major's political press secretary, in a rare insight into the workings of the News International press baron.
She said: "It was made plain to us, the Conservatives, that Mr Major's stance on the single currency was a key factor for Rupert Murdoch in deciding which party to back at the last election.
"The implication was very clear to Mr Major that if he changed his policy and came out firmly against joining the single currency in the first wave there was still a possibility that the Sun would back the Conservatives."
Miss Gunn, a former journalist on the Murdoch-owned Times, said it was very noticeable that Mr Blair became more sceptical in Europe as the campaign went on. And it was immediately after the Labour leader wrote a Euro-sceptical article in the Sun that the newspaper pledged its support.
Mr Murdoch, who is not based in the UK, attended one of a number of meetings Mr Major held at Chequers for editors during the campaign.
The revelation comes at a time when the Government is coming under increasing pressure to tackle Mr Murdoch's domination of the media in Britain. Rebel Labour peers joined forces with the Opposition this week to defeat the Government and defend newspapers including The Independent and the Daily Telegraph from predatory pricing tactics by the Times which sells at below cost price.
Mr Blair has persistently denied that he cosied up to Mr Murdoch in the run-up to the election. But it is well-known that Alistair Campbell, his chief press adviser, pinpointed the importance of support by the Sun early in the campaign. And the nature of relations between Mr Blair and Mr Murdoch is likely to be resurrected on the back of Miss Gunn's comments.
In the 1992 general election, the Sun, News of the World, the Times and the Sunday Times all supported the Conservatives. But in 1997 only the Sunday Times remained loyal.Reuse content