Congressional Democrats seized on trade yesterday as a potentially powerful political issue, switching from attacking Japan for its protectionist policies to blaming the Reagan administration for the United States' record trade deficit.

House Majority Leader Jim Wright Jr. (D-Tex.) said that both the trade and the budget deficits are "growing like cancer cells" and asserted that President Reagan "has abdicated responsibility and refused to assert leadership necessary to solve either problem."

Wright made his statement as he announced the appointment of a Democratic task force on trade that will hold hearings across the country and propose legislative initiatives for Congress. The task force is headed by Rep. Don Bonker (D-Wash.), chairman of the Foreign Affairs Committee's international trade subcommittee, with Rep. Sam Gibbons (D-Fla.), head of the trade panel of the House Ways and Means Committee, as cochairman.

Across Capitol Hill, Sen. Lloyd Bentsen (D-Tex.), ranking minority member of the Senate Finance Committee's trade subcommittee, also attacked Reagan administration trade policy, saying that it lacked central direction.

"It's ridiculous that our president doesn't get involved," said Bentsen, who heads a Senate Democratic group studying the trade issue. That task force plans to have its report out within a month, in time to have a possible impact on the president's discussions with other world leaders at the May economic summit in Bonn.

Senate Republicans such as John C. Danforth (R-Mo.), chairman of the Senate Finance Committee's trade subcommittee, also have attacked the Reagan administration in committee hearings over the past week for failing to have a coherent trade policy.

Trade was discussed as a possible political issue at recent retreats held by House and Senate Democrats.

The Democratic moves to raise the profile of trade as a political issue come during a week of intense interest in the subject. Congress is approaching a boiling point over what it sees as Japan's refusal to allow American companies the same rights to sell in its market as Japanese companies have in the United States. Both the House and the Senate urged the president in nonbinding resolutions this week to retaliate against Japan, which had a $36.8 billion trade surplus with the United States last year.

Danforth said the point of those votes was to send a message to the White House, not Japan as it had been widely believed, that Congress is serious on the trade issue and wants the administration to use powers given to it last year to act against trading partners who place restrictions on American sales.

Danforth, Bentsen and Sen. Frank R. Lautenberg (D-N.J.) announced yesterday they will introduce legislation after the Easter recess that could restrict imports of telecommunications equipment from Japan if that country fails within six months to give American companies equal access to its newly denationalized telecommunications market. Other countries face similar bans, but the time span before they take effect is longer.

Japan reacted to this intensified congressional pressure by sending a special envoy, Deputy Foreign Minister Reishi Teshima, to Washington to explain Tokyo's position to the administration and Congress. Teshima arrived here yesterday afternoon and immediately went to Capitol Hill, where he met with Bonker for almost an hour.

"I told him that we in Congress are at the end of our rope on negotiations," Bonker said. "We are not interested in more talk, more negotiations, more delays. We want to see results."

Earlier, Majority Leader Wright said he hoped Teshima will return to Tokyo "with a clearer understanding that the time is past when the United States will continue to tolerate the unfair trade practices that exclude our goods from their markets" while "we permit their goods to be sold in our markets."

"A new age has dawned," Wright said, "and the United States demands reciprocity in its truest sense."

Despite Wright's strong language, Bonker and Gibbons insisted the Democratic task force is not aimed at Japan. "We're seeking a broader solution, not just an anti-Japanese stance," said Gibbons.

Bonker urged presidential action against Japan if it does nothing to ease the imbalance, which most specialists expect to worsen this year. "If the president refuses to exercise the authority he has," said Bonker, "then I expect Congress will have to step in."

Treasury Secretary James A. Baker III, however, warned Congress against a trade war that he said could hurt the United States. "We do need more access to Japanese markets for beef and agricultural products and telecommunications and a lot of other things. I'm just not sure the way to get there is to have an all-out trade war," Baker told the Senate Appropriations subcommittee on foreign operations.

He chided Sen. Arlen Specter (R-Pa.) for suggesting a ban on Japanese imports that exceed U.S. sales in Japan, calling the idea "outright protectionism."