David Cameron’s plans to redefine marriage are “divisive” and “ill thought through”, senior Tory Dr Liam Fox says.
In a letter to constituents, Dr Fox also says the plans threaten the freedom of churches and he will vote against it.
And Energy Minister, John Hayes, also says he will vote against the proposal because marriage is the best place for raising children.
Senior Labour MP, David Blunkett, has also called the plans a “complete dog’s dinner” and says he will listen to the views of voters.
Dr Fox says in his letter that redefining marriage “smacks of a form of social engineering of which Conservatives should be instinctively wary.”
He adds: “I believe these proposals are divisive, ill thought through and constitutionally wrong.”
The number of Tory MPs set to vote against the Government is growing ever larger, with more than 130 opposed to the plans so far.
The House of Commons is expected to get its first opportunity to vote on the issue in the next few weeks.
One million leaflets against the plans have been sent to voters in key constituencies, most of them marginal seats.
The leaflets have been produced by the Coalition for Marriage, which is campaigning against the Government proposals.
Even if the Government wins in the Commons, it can expect a tough battle in the House of Lords.
According to recent polling, most peers in the Lords think the plans should be shelved because there isn’t enough public support.
And an even stronger majority is opposed to any attempt by the Government to ram the measure through using the Parliament Act.