Peter Tatchell estimates that between 50,000 and 100,000 gay men were convicted of “victimless offences” between 1885 and 2003 and has urged the government to “right this historic wrong”.
While the government has no plans to grant pardons, it has announced plans to disregard the offences on criminal records.
Currently, they can be viewed on police records and also show up on CRB checks, which are used in some kinds of employment such as working with children or vulnerable people.
Mr Tatchell said: “Instead of tinkering with the criminal record system, the government should grant a full pardon to all men convicted of consenting homosexual behaviour that has ceased to be a crime.
“In 1989 alone, there were over 2,000 convictions for the consensual gay offence of ‘gross indecency’ – an offence that only applied to sexual contact between men and not to comparable heterosexual behaviour.”
He added: This pardon should embrace not just men convicted of sexual acts, but also those who were convicted for mere loitering, chatting up, looking at other men, exchanging names and addresses, aiding and abetting gay sex and the myriad other discriminatory, homophobic laws that remained on the statue book until 2003.”
The provisions in the Protection of Freedom Bill will “delete” the offences, the government said last week.
But Mr Tatchell claimed: “Contrary to what the Home Office is suggesting, the government is not planning to delete past gay convictions for consensual offences. Clause 85 of the Protection of Freedoms Bill merely instructs the police to disregard them. This is not the same as deleting them.
“The convictions will remain in the criminal record but they will not have to be disclosed and the police and other agencies will not be allowed to cite them or use them against a person when they apply for a job or get stopped in the street.
“However, the convictions will still appear in police files and could influence police perceptions of a gay person who they question on an unrelated matter.
A Home Office spokesman told PinkNews.co.uk on Friday: “We can categorically assure any man wishing to have his name cleared of an out-of-date conviction it will be wiped from all police databases and will never appear on a criminal record check.
“Where the age of the conviction means it was recorded in a historically important document, often containing details from other cases, we are unable to physically destroy it.
“But it will be marked disregarded and will not appear on any police database once officially deleted.”