Seven House Democrats yesterday asked President Reagan to repudiate the National Republican Congressional Committee's "irresponsible, mean-spirited partisan attack" on them after they opposed a conservative-sponsored amendment to the International Monetary Fund authorization bill.

All seven supported the IMF bill when it was approved by six votes in the House earlier this month, and they warned Reagan in a letter that the Republican campaign committee's tactics could threaten final congressional approval of the $8.4 billion funding bill, which the White House badly wants enacted.

One of the Democrats, Rep. Jerry M. Patterson (D-Calif.), is prepared to change his vote because of the NRCC's action, and sent a letter to Reagan on Wednesday saying, "Unless the statements by the NRCC are forcefully and effectively rebutted, this legislation will not pass."

It was not clear whether others who signed yesterday's letter would change their votes.

The seven had opposed an amendment offered by Rep. Phil Gramm (R-Tex.) that prohibited U.S. support for IMF loans to communist dictators. The amendment was approved, 242 to 185. But among the opponents were the White House, House Minority Leader Robert H. Michel (R-Ill.) and the ranking Republicans on the House Banking, Finance and Urban Affairs and the Ways and Means committees.

After the vote, the NRCC sent press releases into the districts of about 20 Democrats who opposed the amendment. The release said the Democrats had voted to lend taxpayers' money to communist nations. It quoted Gramm as saying, "What gives them the right to support communism?"

Noting that they had supported the president's position on the amendment, the seven House Democrats wrote to Reagan, "By condemning many Democrats for opposing the Gramm Amendment, the NRCC was also condemning you, and many of its own congressional leaders."

The letter to Reagan concluded with a request that he disassociate himself from the NRCC's actions.

"At the very least, those of us who have been targeted with this demogogic attack deserve assurances from you that our support for administration positions will not again be distorted for political purposes," the seven wrote.

The letter was signed by Reps. Patterson, Howard E. Wolpe (D-Mich.), Jim Moody (D-Wis.), Dante B. Fascell (D-Fla.), Robert A. Young (D-Mo.), Katie Hall (D-Ind.) and Thomas R. Carper (D-Del.).

A White House spokesman said he had no comment on the letter.

The letter was organized by Wolpe, who was in Africa yesterday. His press secretary, Stephen J. Gools, said Wolpe will continue to support the IMF bill even if Reagan does not apologize.

"Mr. Wolpe had held from the first instance that the IMF bill was important both to the international economy and to our own foreign policy interests," Gools said.

Earlier this week, Rep. Fernand J. St Germain (D-R.I.), chairman of the House Banking Committee, wrote Treasury Secretary Donald T. Regan warning that the IMF bill, which is now before a House-Senate conference, was not likely to win congressional approval unless the administration helped push a housing authorization bill supported by St Germain through the Republican-controlled Senate.