LONDON, NOV. 1 -- Geoffrey Howe, the most senior member of Prime Minister Margaret Thatcher's cabinet and the one most at odds with her over Britain's role in the European Community, tonight resigned as deputy prime minister, plunging her government and the Conservative Party into a new political battle over a united Europe.

Howe, who surprised Thatcher by tendering his resignation at a 30-minute meeting this evening, became the latest in a string of senior ministers to quit the cabinet over the issue of Britain's ties to the continent.

In a brief letter of resignation, Howe expressed concern that Thatcher's outspoken and abrasive recent performance in opposing further economic and monetary union would isolate Britain from the rest of the European Community, weaken its influence and divide the country and the party.

"I am deeply anxious that the mood you have struck . . . will make it more difficult for Britain to hold and retain a position of influence in this vital debate," he wrote to her. "The need to find and maintain common ground on the European issue within our own party will be crucial to our electoral success and the future of the nation."

From Thatcher's viewpoint, the timing of Howe's resignation could not have been worse. The Conservatives have slipped more than 15 points behind the opposition Labor Party in recent polls, inflation has climbed to nearly 11 percent and this week the Confederation of British Industry declared the country was in a "deep recession."

Howe's resignation was a dramatic signal of the growing battle in Britain over the shape of the new Europe that will emerge in 1992 when the 12 members of the European Community are scheduled to integrate their economies and monetary systems. Both Conservative and Labor parties remain deeply divided over Britain's future in Europe.

Thatcher, arguing that British sovereignty is at stake, long has been suspicious of a federalized Europe because she fears her country will lose both power and freedom of choice if it becomes part of a monolithic Europe likely to be dominated by Germany. Howe and other supporters of a united Europe fear Britain will lose influence and be reduced to the status of a middle-ranking power if it does not join the coming European economic bloc.

Two days ago, Howe sat ashen-faced and silent in the House of Commons as Thatcher launched a bitter attack on the other states in the European Community and defended the defiant stand she had taken at a meeting of heads of state in Rome last weekend. She said plans to introduce a single European currency and to accelerate economic integration would "destroy democracy" by depriving states of sovereignty and she promised to veto any such attempts.

Thatcher also made clear that she intended to raise the European issue as a major plank in the next parliamentary elections, scheduled to take place by the summer of 1992. Several senior Tories, including former defense secretary Michael Heseltine, her main party rival, have warned that such a move would split the Conservatives.

Downing Street officials said Thatcher told Howe she accepted his resignation "more in sorrow than in anger." But in her reply letter, she said she believed the party was united in wanting to preserve the sovereignty of Parliament.

Howe, the last remaining member of Thatcher's original cabinet, formed in 1979, had seen his influence wane greatly in the last year since she removed him from the post of foreign secretary. Still, he was a figure of stature and experience whose support of speedy integration with Europe made him a major spokesman for the pro-European wing of the party.

One unanswered question tonight was whether his resignation would trigger a new leadership challenge to Thatcher from within Conservative ranks. Howe insisted in his letter that he would still support the government, but friends said he was considering whether to throw his support behind another Tory willing to stand against her in the annual party caucus next month.

All of these factors have caused deep anxiety within the ranks of the party, as did the loss of a supposedly "safe" Conservative House of Commons seat two weeks ago in a special election. Many Conservative lawmakers fear they could head into the next election in the midst of an economic slump and led by an unpopular prime minister.

But while the economy has made these lawmakers uneasy, Europe has been the chief issue dividing them and sending shock waves through Thatcher's cabinet. The question of whether to adopt a single European currency -- a move that would mean the death ultimately of the beloved British pound -- has become an emotional rallying point for those wary of closer ties to the continent.

Most of those in the pro-European faction within the party also oppose a single currency, but believe Britain must take a cooperative attitude with its European partners or become weakened.

Thatcher lost her chancellor of the exchequer, Nigel Lawson, last fall due to her refusal to join the European exchange rate mechanism and link the British pound to other currencies. Her closest ministerial ally, Nicholas Ridley, was forced to quit last summer when he made anti-German remarks.