Tory activists have urged the House of Lords to reject the same-sex marriage bill in Tuesdays vote, arguing it will weaken the bringing up of children and devalue the family.

In a letter to the Sunday Telegraph, Conservative Grassroots Chair Robert Woollard writes in opposition to marriage equality: “The golden inheritance of every previous generation, that has been lovingly handed down to us, is now being smashed on the anvil of ‘equality and fairness’.

“Is this the ‘new intolerance’?” he asks.

This scathing criticism of the Government’s push for same-sex marriage follows just one day after David Cameron received a letter from 53 Christian, Jewish, Muslim, Hindu and Buddhist leaders, which said that the legislation would lead to “injustice and unfairness” and accused him of rushing through the bill.

Mr Woollard contends that Cameron made “a shabby deal with Labour” to overcome hurdles in the House of Lords. He also accuses him of coercing his party to support the bill, despite claiming to give a free vote on the matter.

Quoting Cameron’s argument that “enabling same–sex couples to get married will strengthen – not weaken – family ties”, Mr Woollard counters: “All the evidence from countries that have introduced this legislation over the last ten years shows that marriage is further devalued in the eyes of all and the tie between marriage and bringing up of children is seriously weakened.”

For Mr Woollard, creating an environment for raising children seems the crux of the matter. He argues that many Tory party members who “have had the responsibility of bringing up children themselves” oppose the bill, as they believe it goes against family values.

Next week’s House of Lords vote on the Marriage (Same Sex Couples) Bill will now take place on Tuesday in the daytime, after supporters warned voting in the early hours could put the bill at risk. 

On Wednesday, Baroness Thornton warned against allowing next week’s House of Lords second reading debate on the Marriage (Same Sex Couples) Bill to drag on into the late hours.  

With at least 86 peers having requested to speak on Monday, the vote was predicted to go on as late as 3am.