Local Conservative party chiefs are descending on Downing Street as the party faces a major split on gay marriage.
Months of opposition to the coalition's plans to legalise same-sex marriage are coming to a head this week ahead of the first parliamentary debate of the marriage (same sex couples) bill on Tuesday.
Current and recent Conservative association chairmen will present a letter signed by over 20 senior local Tories to No 10 this lunchtime in which they register their concern at the "discord" created in the party by the issue.
Some Conservatives had hoped the gay marriage legislation could have been counterbalanced by moves to introduce tax breaks for married couples - a Conservative proposal in the 2010 manifesto which has not yet been implemented by the coalition.
Yesterday it was confirmed the move would not be included in next month's Budget, however.
"Many of us feel a huge sense of personal betrayal over these plans," said Ed Costelloe, who resigned as chairman of the Somerton and Frome Conservative association, a key target seat at the next election, last week.
"We worked hard locally to convince people to support Conservatives but this was not part of the platform. There was no mention of this in the manifesto. We don't know where this has come from or why it has become such a priority given so many other pressing issues.
"We are also shocked by the way in which it being it is being pushed through with so little regard for proper scrutiny."
Costelloe's claim that the issue is "certainly not a vote winner" seems vindicated by a poll this weekend by ComRes, which found 20% of those who voted Tory in 2010 would rule out doing so if the party backed same-sex marriage.
A majority of Conservative MPs in parliament are likely to vote against the measure on Tuesday. Downing Street has conceded the legislation will be a free vote, meaning Tory opposition will not technically be a rebellion. But backbenchers are full of resentment against the whipped programme motion outlining the timetable for the bill in the Commons.
Around 180 Tory MPs, including environment secretary Owen Paterson and Welsh secretary David Jones, are expected to vote against the bill, according to the Sunday Telegraph.
That leaves just 120 Conservatives backing the prime minister on the issue. Foreign secretary William Hague told BBC1's Sunday Politics programme: "Marriage is an institution which is a very positive institution in our society. We shouldn’t deny it to people on a discriminatory basis."
Conservative Future, the youth branch of the Tory party, has dispatched letters to Conservative MPs signed by seven of its senior members calling on them to support the legislation, the Independent on Sunday reported.
And Michael Fabricant, the Conservative party vice chairman, tweeted: "I really don't know why a vocal minority have got their [k]nickers in a twist over Gay Marriage."
Despite splitting the Tories, the bill is likely to progress through the Commons unhindered thanks to support from Labour and the Liberal Democrats.
Rebellious Conservative backbenchers are unhappy with the prime minister over his handling of the boundary changes defeat last week, in which Labour and the Lib Dems teamed up to block a reform which would have handed the Tories the equivalent of an extra 20 seats at the next general election.
Stewart Jackson told the Independent on Sunday newspaper: "I hold David Cameron, his arrogant disregard for the views of opponents, and political misjudgement responsible for this disastrous mess."