London — Britain's opposition Labour Party, struggling to close the commanding opinion poll lead of the ruling Conservative Party, has retreated from one of its key general election pledges. If Labour wins the general election June 9, it will not automatically phase out Britain's independent nuclear deterrent.
Instead, Labour is proposing the British Polaris submarines become a bargaining chip to improve the chances of progress in East-West arms control negotiations in Geneva.
The party's new posture was approved by the Labour leader, Michael Foot, after a bitter backstage wrangle from which the deputy leader, Denis Healey, emerged the victor.
Concerned at the Conservatives' opinion poll lead - between 10 and 18 percent , according to the latest polls - Healey told Foot he could not fully support him on the hustings unless the party ''clarified'' its stand on nuclear weapons.
Foot sympathizes with Labour leftists who want to get rid of Britain's nuclear deterrent quickly. Healey, who was defense secretary under Harold Wilson , has been urging a less radical approach. He is strongly backed by moderate sections in the party.
The formula, which emerged from urgent private consultations, pledges a Labour government would cancel purchases of the US-supplied Trident missile designed to replace Polaris, and reject American cruise missiles on British soil. But it would leave Polaris afloat and on station.
Healey has found during campaigning around the country that many voters believe Labour's unilateralist policies, if put into effect fully, would leave Britain at a disadvantage internationally.
Conservative Prime Minister Margaret Thatcher has argued the same case. So has David Owen, who was foreign secretary in the last Labour government and is now the defense spokesman for the Social Democrat Party-Liberal alliance.
Owen declared: ''Labour's defense policies would make them unfit to govern. The British people are not stupid and when they see the defense policy of the Labour Party, they shudder. They actually think it is dangerous, and a great majority of people use that word.''
To allay these fears, Healey proposed that Labour switch the emphasis of its unilateralist policies. In a statement Healey said, ''Labour will cancel Trident and stop cruise and move towards the establishment of an effective nonnuclear defense policy. Labour will put Britain's Polaris force into the nuclear-arms talk so that Britain can take its proper seat at the negotiating table.''
[Foreign Minister Francis Pym said May 25 the Tories would consider including Britain's nuclear weapons in the Geneva talks.]
Some pollsters are suggesting that unless Foot and his followers find a way of impressing voters, Mrs. Thatcher will enjoy a majority of at least 100 seats in the next Parliament.
Labour's retreat on Polaris produced dismay among left-wing activists who argue that their party manifesto (the document outlining key policies) proposes early dismantling of all British nuclear-weapon systems.
In a move related to the Polaris backtrack, Labour officials have decided that their party will make no precipitate moves to slash defense spending if it returns to power. Labour initially proposed spending should be cut from the current 5.1 percent of the gross national product to 3.5 percent. Mrs. Thatcher claimed that would mean the loss of 400,000 jobs in defense-related industries.
Labour's defense spokesman, John Silkin, replied his party would make no defense cuts until economic growth in Britain occurred