Downing Street said that Charles Wardle, a minister at the Department of Trade and Industry, who was at the Home Office until last summer, tendered a letter of resignation yesterday afternoon.
Government sources also indicated that disagreement with Government policy over immigration - an area for which Mr Wardle had been responsible until last year - was the reason he gave for leaving the Government.
Today's Sunday Express claims that Mr Wardle's departure - the second ministerial resignation in a week - was prompted by his concern that an opt-out from European agreements on migration, negotiated in 1985, was ineffective and likely to be overturned by the European Court.
The agreements involved moving towards a Europe without internal frontiers. The paper said that Mr Wardle feared that this would lead to a substantial influx of non-EU immigrants into Britain.
Although it does not quote the minister, the Sunday Express says that Mr Wardle intends to campaign from the backbenches. He wants the issue on the agenda for the next Inter Governmental Conference in 1996.
The resignation appeared to be the first voluntary departure from Mr Major's government over Europe. But Westminster sources played down its political significance.
Mr Wardle, aged 55, has been identified more as a pro-European than as a Euro-sceptic, and is a friend of the Chancellor, Kenneth Clarke. Moreover immigration has not featured high on the complaints of the Tory right recently.
His colleagues conceded that the minister had been exercised about the rising tide of immigration, but pointed out that he had not chosen to leave the government while serving at the Home Office. One said that immigration was "a pretext".
MPs and minister were surprised by the resignation. But one said that it had been preceded by a "period of considerable personal stress".
While immigration minister, Mr Wardle was embroiled in several high profile areas, including the application for British citizenship of Mohammed Al Fayed. It later emerged that Mr Wardle and Mr Howard had both tried to avoid taking a decision in the case. Relations between the two men were said to be poor.
One ally said that Mr Wardle, who has represented Bexhill and Battle since 1983, had regarded the later part of his tenure at the Home Office as "not a particularly happy one".
But Mr Wardle may have been even more frustrated after he was moved to the DTI.Reuse content