Gay rights activist Peter Tatchell has promised to be on his “best behaviour” while marching alongside the prime minister’s wife at Pride on Saturday.

In a statement, he praised Sarah Brown’s participation in the parade, saying he was “delighted” at her choice to march.

He said: “I won’t embarrass her. I will be on my best behaviour.

“But I do plan to remind Sarah that she and Gordon were able to get married, whereas gay couples cannot. Her husband supports the ban on same-sex marriage. He won’t give lesbian and gay partners the same right to marry as him and Sarah have enjoyed.

“I hope Sarah will be persuaded that the time has come for marriage equality, and that she’ll have a word in Gordon’s ear when she gets back to Downing Street after the parade.”

Tatchell has claimed he was barred from attending a Pride reception hosted by London mayor Boris Johnson on Monday and the forthcoming reception at Downing Street on Saturday morning before the parade.