The former chief constable of the West Midlands, Lord Dear, has warned of a growing House of Lords rebellion over the government’s same-sex marriage bill for England and Wales.

The independent peer is convinced the Marriage (Same Sex Couples) Bill could be rejected by the House of Lords.

According to the Telegraph, he said there was a growing belief in the Lords that even though MPs were given a free vote on the bill – its large Commons majority secured in February’s second reading was thanks to unofficial “arm twisting”.

On 5 February MPs voted 400 to 175 in supporting the government’s Marriage (Same Sex Couples) Bill – a majority of 225 votes – following an afternoon of heated debate in the House of Commons.

The bill completed its committee stage on 12 March 2013 and is due to have its report stage and third reading by MPs on a date to be announced.

In a letter to more than 400 peers delivered over the weekend, Lord Dear criticised the way David Cameron “shunted” the bill through “a very one-sided” Commons committee stage after “wholly inadequate” scrutiny in the Commons.

He said his initial soundings suggested there was a real possibility that the bill could now “go down” in the Lords despite support in the Commons.

“The thing that really bothers many is that the normal process for something as potentially divisive as this has not been followed.”

“The feeling in the Lords is that although (in the Commons) the whip was officially declared not to be on there was a lot of arm twisting going on.”

Lord Dear served as chief constable of the West Midlands until 1 April 1990, when he was appointed an inspector of constabulary.

He was described by the late broadcaster Sir Robin Day as “the best known and most respected police officer of his generation”.