AUGUSTA — Maine Gov. Angus S. King vetoed his first bill of the legislative session Tuesday. He informed lawmakers in a letter that he opposed the proposed repeal of a current law requiring retailers to post gas prices outside their establishments.

The measure, which drew close votes in the House and passed by a wider margin in the Senate, attempts to address a law passed in the 1980s when gasoline stations were offering different prices for credit and cash sales. Reasoning consumers could be confused by the two prices, the Legislature required dealers to post both prices prominently.

But supporters of the repealing legislation maintain the need for such posting has passed and the Legislature’s Business and Economic Development Committee gave the measure a unanimous ought-to-pass recommendation.

King pointed out that while he was anxious to remove unnecessary requirements imposed on Maine businesses, he was equally anxious to ensure that Maine consumers are provided with every reasonable opportunity to be well-informed consumers. King said he sincerely believed that supporters of the repeal proposal, LD 455, shared his objectives.

“However, given the unique market fluctuations inherent in the petroleum industry more emphasis on price disclosure is better than less,” he said.

The governor said he had received many letters and listened to numerous arguments reflecting both sides of the issue, particularly those voiced by the fuel industry, which maintains there are certain costs and inconveniences associated with the requirement that prices be posted at the pump.

“I’ve not been persuaded that these costs and inconveniences warrant repeal of this consumer awareness policy,” he said.

King told legislative leaders that gasoline is a product that all Maine residents rely on in one way or another and that everyone appreciates the efforts required by those selling fuel to keep the public informed, particularly in the area of full price disclosure.

“Therefore, I am vetoing LD 455 and respectfully urge you to sustain my veto,” King wrote in a letter to lawmakers.

Democratic leaders were reviewing King’s remarks late Tuesday afternoon before offering a response, but Republican leaders were clearly not happy even though the vote did not reflect partisan divisions.

“I think it’s up to the marketplace to help inform consumers,” said Assistant House Republican Leader Richard Campbell of East Holden. “I don’t think it’s a function of state government to tell businesses how to inform their customers.”

Given the 100 votes needed in the House and 25 in the Senate to meet the two-thirds support needed for an override of the governor’s veto, such legislative action was perceived as unlikely when the bill passed 76-67 in its final House roll call vote. The Senate supported the bill 21-11.

A vote to override could be taken as early as Thursday.