London — Britain's role in the European Community and its contribution to West European defense are shaping up to be central issues as Prime Minister Margaret Thatcher and her political rivals intensify their battle for the British vote.
With polling set for June 9, the Labour opposition led by Michael Foot is doing all it can to sharpen the general election focus on the state of the economy - notably, the more than 3 million unemployed who are the chief human by-products of prolonged economic recession.
Mrs. Thatcher, aware that unemployment is the weakest point in her party's case for reelection, is determined to highlight what she sees as Labour's more serious shortcomings.
Tory election posters are reminding voters of the Labour Party commitment to negotiate Britain's withdrawal from the European Community. Equal weight is given to Mr. Foot's personal backing for unilateral nuclear disarmament and a defense policy which, if implemented, would remove United States military bases from British soil and stop the deployment of US cruise missiles there.
In between the Conservatives and Labour is the Social Democratic Party (SDP)-Liberal alliance. Roy Jenkins, leader of the SDP, and David Steel of the Liberals claim that the two established parties are advocating extremist policies, and that the solution lies in a vote for ''the sensible and responsible center.''
The quarrel over membership of the European Community seems certain to produce a rising tide of rancor as polling day approaches. Mr. Foot has claimed that Britain could survive and prosper outside the Community and cites Sweden, Switzerland, and Austria as examples of countries which do already.
Mrs. Thatcher's officials have an answer to these claims: Negotiating Britain's exit from the 10-nation club in Brussels would be a bitter experience, with the West Europeans trying to strip Britain of its present membership advantages.
According to one estimate, since 1973 the value of British exports to the Community has risen by nearly 500 percent, compared with a rise of 300 percent to the rest of the world. Nearly twice the quantity of goods are exported to the EC as to the US, Japan, and the British Commonwealth combined.
Disrupt the Community trade nexus, Mrs. Thatcher argues, and you plunge Britain into a far worse economic recession than the present one. Labour politicians admit that withdrawal would probably require any British government to impose import controls and to borrow heavily from the International Monetary Fund, at least for some time.
The dispute between the Tories and Labour on defense policy is promising to be even more vitriolic than the argument about Community membership.
The Thatcher government is committed to replacing non-NATO Polaris missiles with the US-supplied Trident missile. It wants to allow the US to deploy cruise missiles in Britain if there is no progress at the US-Soviet talks in Geneva.
Mr. Foot and Labour spokesmen generally argue that Trident is unnecessary and that involvement in cruise missiles would be a source of danger to Britain. Critics charge that such policies in the Labour Party manifesto and supported by the Labour movement generally would weaken Britain's commitment to the defense of Western Europe.
Mr. Foot insists that Labour would keep Britain strong in conventional weapons, but Mrs. Thatcher continues to taunt him with the jibe that a unilateralist posture is a weak one with which to confront a potential aggressor.
So keen has Mrs. Thatcher been to exploit what she perceives as weaknesses in Labour's policies that some of her aides are warning her to be less strident in her criticisms. It is enough, they say, to point to Labour's policies and let the electorate draw its own conclusions.
Labour and the SDP-Liberal alliance, meanwhile, are inclined to hope that it may be enough to draw attention to Mrs. Thatcher's record on unemployment and her apparent failure, after four years in power, to get Britain back to work again with her monetarist policies.