Activists in Cleethorpes, unhappy after Mr Brown admitted not registering his payments as a lobbyist for a United States tobacco firm for several years, are canvassing the electorate to see whether the party risks defeat if he stands as their candidate.
One source said: "Over the weekend there were a number of telephone calls to see what our stand should be. We want to find out what the electorate thinks."
If the association dissidents decide that the seat, where Labour need only a 6 per cent swing, is vulnerable if Mr Brown stands they will push for a new candidate at the formal adoption meeting on 11 April.
It also emerged that Mr Brown, who has been keeping a low profile in the area over recent days, survived moves to make him face reselection at the association's annual general meeting a year ago.
Melanie Dickerson, a former councillor who unsuccessfully tried to become association chairman at that meeting, said: "There were moves then that Michael Brown should go before a selection committee. At the end of the meeting there was a vote on a show of hands [when] people were asked if they were for Michael Brown - no one was asked if they were against.
"A number of people had already left in disgust. It was a messy vote."
Ms Dickerson is the second senior association member to question publicly whether Mr Brown should stand at the election. Last week councillor Peter Mills warned he would call on the MP to stand down unless he could explain the allegations against him.
Sir Gordon Downey has still to deliver his verdict on Mr Brown, who admitted last year to taking pounds 6,000 for lobbying work for US Tobacco in the late 1980s but not registering the payment for several years. Mr Brown said he had been misled into thinking that disclosure was unnecessary.
Describing herself as a "true blue" Tory, Ms Dickerson said the MP's presence threatened what should be a comfortable Conservative win. "With him as candidate I think we have lost it. Over the last two years he has got very arrogant. He feels he has got a safe seat and does not want to listen to ordinary members of the constituency any more."
She said Cleethorpes was a "sleepy hollow" where people did not readily understand why a well-paid MP should take money for lobbying - especially from a tobacco company.
However, many senior local Tories insist Mr Brown is still their best hope of retaining the seat.
Constituency association chairman Brian Knight has described Mr Brown as an excellent MP and said they had full confidence in him. "I fully expect him to be adopted as our MP," he added.
Meanwhile another Tory MP under pressure, Piers Merchant, looks certain to win formal adoption at a meeting of his party association in Beckenham, Kent, tonight following his well-publicised relationship with a 17-year- old Soho nightclub hostess.
Mr Merchant was overwhelmingly backed by an emergency meeting of the executive committee of the association on Saturday, after it had shown clear irritation at attempts by Central Office to force their hand over the MP's future.Reuse content