The government is reported to be attempting to compromise with the 150 Tory MPs set to oppose the same-sex marriage bill, by considering amendments giving protection to “conscientious objectors”.

MPs are to resume debate on the same-sex marriage bill tomorrow, and if approved on Tuesday it will pass to the House of Lords for further scrutiny.

The Times reports that, of those MPs, around 150 Conservatives are planning to defy David Cameron by opposing the bill or backing amendments to it, among them Cabinet Ministers.

Defence Secretary Philip Hammond already voiced his opposition to the bill in a Question Time appearance last week, in which he said the bill had “upset vast numbers of people”.

Secretary of State for Environment, Food and Rural Affairs Owen Paterson, Lord Chancellor and Secretary of State for Justice Chris Grayling, and Cabinet Office Minister John Hayes are also expected to back amendments to the bill allowing teachers, registrars and faith schools leeway not to uphold the bill if they conscientiously object to it.

Compromises taking place behind the scenes in Parliament may result in amendments allowing teachers not to include same-sex relationships in their lessons, and permitting registrars not to marry same-sex couples, in order to keep as many Tory MPs on board as possible.

A source told the Sunday Times the government is “in listening mode” when it comes to marriage equality objections, and that they were trying “to plug some of the gaps before it goes to the Lords.”

Amendments were tabled by Conservative MP David Burrowes, who last week called for a referendum on same-sex marriage, adding that he hoped it would result in the defeat of the Marriage (Same Sex Couples) Bill.

There have also been calls for the bill to allow opposite-sex couples to be able to have civil partnerships. The move is opposed by the government, but last week Culture Secretary Maria Miller allowed that a review on civil partnerships would take place exactly five years from the point when the same-sex marriage bill comes into law for England and Wales.

The debate has caused embarrassment for David Cameron and was labelled an attempt to “derail” the same-sex marriage bill by Tory MP Mike Freer, while LGBT rights activist Peter Tatchell said a review of civil partnerships for straight couples was unnecessary, as the idea already has public support.

In a letter to David Cameron this weekend, 30 past and present local Conservative chairs from the party’s Grassroots organisation warned that his push for same-sex marriage had made winning the general election “virtually impossible”.