British Defense Minister Michael Heseltine today pledged that the Conservative government would not abandon plans to build new U.S.-designed Trident missile submarines and attacked the "curious morality" of the opposition Labor Party's commitment to unilateral nuclear disarmament.

"No responsible government would abandon the insurance policy that is our last resort guarantee against nuclear blackmail" by the Soviet Union, Heseltine told the annual Conservative Party convention here.

The $11 billion price tag for four vessels to replace the aging Polaris fleet would be spread over 20 years and should be seen in the context of total defense spending over that period of perhaps $450 billion, he said.

The Trident costs have made the project very controversial and the ruling Conservatives are the only party pledged to support it.

Conservatives here argued, therefore, that they are the only party "that stands for deterrence," as one speaker put it. Although the two Alliance parties -- Liberals and Social Democrats -- favor retaining Polaris, in part as a bargaining chip in arms talks, the Conservatives argued today that without Trident, there will be no deterrent left after Polaris wears out from old age.

Labor's defense spokesman, Denzil Davis, said in London today, "Heseltine will soon be faced with the choice of either canceling Trident or making further slashing cuts in the Army and Navy that would weaken further Britain's conventional defense."

In his attack on Labor's defense policy, Heseltine also called attention to an aspect that has been left officially unclear by Labor.

At its annual conference last week, Labor said if it gained power it would get rid of all British nuclear weapons and all U.S. nuclear weapons in Britain. Nuclear weapons made Britain a nuclear target and nuclear defense was suicidal, Labor said, while pledging itself to maintain strong nonnuclear forces.

But it was not stated whether a Labor government would also reject being defended by American nuclear weapons based in the United States, and this question has now arisen both here and among some dissenters at the Labor Party convention at Blackpool.