OTTAWA (AP) _ Minister of State Roch Lasalle has resigned following allegations that businessmen hoping to win government contracts paid $3,750 each for entry to a party he attended.

Prime Minister Brian Mulroney accepted Lasalle's resignation Thursday.

In a resignation letter submitted Monday, Lasalle, a veteran standard- bearer for the ruling Conservative Party in Quebec province, condemned as ''unfounded'' and ''vicious'' allegations that he did anything wrong.

He later said in an interview, ''I have done nothing wrong. I leave with a clear conscience.

''If there were fund-raising dinners that cost $5,000 ($3,750 U.S.), I never saw anybody pay that amount of money and it certainly wouldn't be proof of their intelligence if they did,'' he said.

Lasalle in his letter that he would remain a member of Parliament but would not seek reelection.

Mulroney wrote Lasalle in response, ''I know to what point the last few weeks have been difficult and trying for you.''

A police probe into the 1985 party Lasalle attended already has led to influence-peddling charges against a Conservative member of Parliament, Michel Gravel, who has yet to stand trial. Lasalle has not been charged.

Lasalle, 57, a minister without portfolio, was the seventh Cabinet minister to leave Mulroney's government since the Conservatives swept to power in September 1984, and the second this year. Four of the seven left because of conflict of interest allegations.

Five weeks ago, another Quebec-based Cabinet member, Andre Bissonnette, minister of state for transport, was fired. Police are investigating a shady real estate deal in his constituency in which land for a projected aerospace factory tripled in value in 11 days.

Two of Lasalle's top aides resigned after it was disclosed that they failed to get security checks and had past criminal records.

Lasalle's departure coincided with the latest public opinion poll, which showed the Conservatives are the most unpopular governing party in the 45 years polls have been taken.

The survey indicated the Conservatives have the support of just 22 percent of the electorate, compared with 44 percent for the opposition Liberal Party and 32 percent for the New Democratic Party.