Members of the House Economic Matters Committee summarily killed a bill today that would have limited to three days the amount of time a financial institution may "float" a person's check before crediting it to that person's account.

The bill would have aided thousands of customers but deprived more than 300 state-chartered banks, savings and loans and credit unions of an estimated $170 million a year -- money those institutions make by investing deposited checks during the float period -- according to Sen. Stewart Bainum Jr. (D-Montgomery), one of the bill's sponsors. That period can be six business days or longer, according to a survey last fall by a Maryland public interest group.

The measure, which earlier had passed the state Senate on a unanimous vote, was voted down 14 to 5 by a committee that has bestowed numerous favors on Maryland's financial industries over the years. The vote reflected a last-minute lobbying effort by committee Chairman Frederick C. Rummage (D-Prince George's), several committee members said.

Bainum, one of the Senate's less animated members, was livid after the House committee vote. "It's not hard for me to believe they bowed to the banking lobby. But to do it in such an open way this close to an election! Well, it takes a lot of nerve."

Rummage said he did not work to scuttle the check float bill, but he acknowledged that he wanted to see it fail.

"We'd be discriminating against our own banks," said Rummage. "If it had applied to nationally chartered banks as well, I'm sure it would have passed unanimously."

Rummage ignored a customary legislative courtesy when he denied a request by several committee members, including two from Montgomery County, to delay the vote on Bainum's bill. One committee member on the losing side suggested that that was because Rummage had seen the hours Bainum spent lobbying for his bill in the House of Delegates lounge this week.

"Fred didn't want Stewart lobbying the committee," said Del. Diane Kirchenbauer (D-Montgomery), a longtime Bainum ally who lives in Bainum's Senate district. "Are banks a protected class in his mind?"

In hearings earlier this session, the lobbyist for the Maryland Bankers Association had criticized the proposed limit as too arbitrary and noted that customers have the right to bank at those institutions offering the shortest check-holding periods. Banks hold checks until they've cleared to protect themselves against bounced checks, the lobbyist said.

But Bainum and consumer group representatives derided float periods as nothing more than infuriating ploys that enable banks to generate income by investing the deposits in money markets.

Michael Caudell-Feagen, a staff attorney at the U.S. Public Interest Research Group, said tonight the death of Bainum's bill will "allow banks to make hundreds of millions of dollars while they're denying customers access to their funds. It's just a consumer scam."

The House committee's action on the check float bill was the latest sign of tension between the two houses as the legislature rushes to complete its work.

A potentially explosive dispute arose over the fiscal 1987 budget, which both houses are required to pass by Monday.

Though each house has adopted its own version of the budget, the differences must be resolved in conference. Conference committee members were refusing to meet this week, but began deliberations this afternoon.