Sen. Edward M. Kennedy (D-Mass.), continuing his efforts to capitalize on the economic issue, yesterday introduced legislation to impose wage-price controls -- the centerpiece of his campaign for the Democratic presidential nomination.

The bill, dropped into the legislative hopper while Kennedy was stumping in Pennsylvania, appeared to be essentially a campaign document. Key congressional leaders still are solidly opposed to controls, and Kennedy has no co-sponsors for the legislation.

The Massachusetts senator took the opportunity to assert in a written floor statement that the controls bill was needed because "responsibility for leadership in confronting our economic problems has passed to the Congress."

"In the face of crisis," he said, "this nation requires extraordinary leadership and extraordinary measures, not paralysis and political opportunism. lAnd yet . . . President Carter has offered measures which are hopelessly inadequate."

The proposal was unveiled as Kennedy, campaigning in Pennsylvania's steel-mill country, lambasted the administration anew for allegedly failing to protect the domestic steel industry from unfair import competition.

In stops at Johnstown and Allentown, the Democratic challenger repeatedly cited the recent rupture between the White House and big steel over Carter's handling of the new "trigger-price" system, and vowed he would act more vigorously.

The trigger-price system was established by Carter in 1977 as a gesture to dissuade leading steelmakers from filing suits that might have limited import levels and disrupted trade relations with major industrial countries.

In essence, the system set minimum prices at which steel could be imported. The idea was to prevent foreign producers from selling steel here at artificially low prices, known to economists as "dumping."

The White-House industry pact ruptured late last month, however, after the administration declined to raise its trigger prices as much as the industry wanted, and U.S. Steel Corporation filed a suit to block further dumping.

In retaliation for the U.S. steel move, the administration suspended the entire trigger-price system, and the battle over dumping is on anew. Many economists regard such import limitations as protectionist measures.

Recalling a Carter speech to Pennsylvanians in 1978, Kennedy quoted the president as having told a Pittsburgh audience then: "'As long as I'm president, we won't have to worry about that (dumping) anymore.'"

Kennedy then added yesterday, "You won't have to worry about that, Jimmy, because we're gonna get you out of the White House!" The dumping issue has been controversial in steel-producing regions.

The legislation imposing wage-price controls contained no major surprises from the informal plans Kennedy has outlined in speeches before. The bill calls for a wage-price freeze of up to six months, to be followed by controls.

Kennedy added one, minor new wrinkle: To minimize the risk that businesses might raise prices in anticipation of controls, the bill would authorize the administration to make the restraints retroactive if it wished.

The restraints would apply to a far broader segment of the economy than the wage-price controls of 1971-73 -- not only to wages and prices, but to rents, dividends, profits and interest rates as well.

Although many economists regard such sweeping restraints as unworkable, Kennedy proposed exempting only two categories of prices -- raw agricultural commodities and imports. Wage and price standards would be set by the president.

Carter and all the GOP presidential candidates have opposed wage-price controls, and so have most mainstream economists. Their argument is that the restraints result in distortions that create added economic problems.

Some prominent economists have endorsed controls in recent weeks, but only as part of a broader package that would include tight budget and credit policies, which Kennedy opposes.

Reporters were told yesterday the Kennedy legislation was introduced mainly to broaden debate over the controls issue. It was not clear yet whether the Massachusetts senator planned to press vigorously for the bill's enactment.