Conservative peer Lord Waddington and Labour backbencher David Taylor MP have called for a ‘free speech’ defence to be kept in a bill designed to criminalise incitement of homophobic hatred.

In a letter to The Times today, Waddington and Taylor cited recent cases of people being pursued by police for making anti-gay statements, such as Norwich woman Pauline Howe who called gay pride marchers “sodomites” and added that homosexuality had “contributed to the downfall of every empire”.

They wrote: “The free speech clause is supported across the political spectrum. Liberty, the Church of England, Matthew Parris and Rowan Atkinson have also joined the ranks of those who back it.”

The clause in question reads: “For the avoidance of doubt, the discussion or criticism of sexual conduct or practices or the urging of persons to refrain from or modify such conduct or practices shall not be taken of itself to be threatening or intended to stir up hatred.”

In June, the House of Lords voted 186 to 133 to retain the amendment, which allows “discussion or criticism” of sexual practices. This includes criticisms of homosexuality and urging gays to turn straight.

The issue has now returned to the House of Commons. In March, MPs voted to remove the amendment in March by 154 votes.

The government has said the amendment is not necessary but campaigners including the Blackadder star Rowan Atkinson and the gay actor Christopher Biggins have argued that the clause relating to hatred in the Coroners and Justice Bill could limit freedom of expression and could lead to prosecutions over gay “jokes”.

Waddington and Taylor’s letter continued: “Some might say it is so moderate that it merely states the obvious and is therefore unnecessary. But those who say that are closing their eyes to what is happening.

“Police officers, pressurised by diversity training and furnished with guidance from the Home Office and the Crown Prosecution Service, seem to feel duty bound to come down like a ton of bricks on people who express disagreement with the behaviour of some gay rights activists, and members of the public are left feeling harassed and frightened.

“The recent case of the Christian grandmother interrogated in her living room about a letter she wrote to her local council is just the latest example. The politically motivated trampling of free speech is something that should concern us all. It is the duty of Parliament to try to prevent this from continuing to happen.”

The new law against incitement to hatred on the grounds of sexual orientation is unlikely to be used frequently.

Similar laws against inciting racial hatred have only been used around 20 times in the 30 years since they came into force.