Democratic attorneys general in Alabama and Illinois have filed suit to stop allegedly deceptive solicitations by the National Republican Senatorial Committee.

In the solicitations, the committee sent $25 checks to prospective contributors as a gimmick. Cashing such a check automatically allowed the campaign committee to begin withdrawing $12.50 a month from an endorser's bank account.

The three-page fund-raising letter stated that by endorsing the check, the recipient agreed to participate in the GOP's "newest candidate support concept called Candidate Escrow Funding (CEF)." The letter noted that signers may cancel the arrangement at any time after two months. Otherwise, it said, the $12.50-a-month payments will continue to be transferred to the committee.

NRSC spokeswoman Wendy Burnley said the committee is confident that the solicitations will withstand a legal challenge because they were checked carefully with the committee's lawyers before an initial test mailing to 300,000 individuals last February and March. A second mailing of more than 700,000, sent during the last six weeks, resulted in complaints and inquiries in several states, including Wisconsin, Oregon and Minnesota. Burnley said committee lawyers met last week with representatives of several state attorneys general and "offered to work with them to address their concerns."

The Alabama suit was filed last week after a complaint from the family of an elderly woman who said she did not realize endorsing the check triggered automatic withdrawals from her account.

On Tuesday, Illinois Attorney General Neil Hartigan, who is running for governor, filed suit seeking "to enjoin the fund-raisers from further deceptive solicitations" and to force them to cancel the repayment authorizations and provide "full restitution." His opponent, Republican Secretary of State Jim Edgar, also denounced the tactic and asked the party to stop using it.

Hubert H. Humphrey III, the Minnesota attorney general, said in an interview yesterday that his office also is considering a suit. "It's deceptive and misleading and sleazy," he said. "Beyond that, it might be illegal. They say, 'Here's $25,' and then in the fine print tell you it will cost you $150 a year. . . . Tricking people to raise political money is just wrong. I wouldn't want Democrats or Republicans to do it."

Don Hanaway, Republican attorney general of Wisconsin, told the Associated Press last week he was "outraged" by the solicitations. "This scheme is unconscionable and ought to be stopped," he said.

The NRSC relies heavily on direct mail to raise money, Burnley noted. She said the $25 check solicitations represented a small part of the committee's mail program and were designed "to try to eliminate the exorbitant cost of printing and postage and to streamline the fund-raising process." The latest mailing went to members of the committee's "Republican Presidential Task Force," who already send in monthly checks of $10 or so, Burnley said. The committee changed parts of the first letter to add a toll-free number to call to cancel the commitment and to drop a reference to increasing the automatic withdrawal by 10 percent after the first year, she noted.

The lawsuits are the latest controversy over NRSC tactics. In July, the committee sent "National Voter Data Cards" to 500,000 individuals, asking them to return a $9 "processing check." The mailing prompted calls to the Federal Election Commission by state election officials and recipients who were "confused and concerned because they thought they had to pay to vote," an FEC spokeswoman said. Last month, the FEC sued the NRSC, contending that by funneling more than $2.7 million to Senate candidates in 1986, the committee violated limits on contributions to single candidates.