Image via Wikipedia
Peter Tatchell said it was "no big deal" he was not invited to the event but questioned why he has never been invited to any Downing Street reception.
Last year, he accused Gordon Brown of personally asking for his name to be removed from the guestlist of one such event, apparently because Mr Tatchell had heckled him.
Mr Cameron will be the first Tory prime minister to hold a reception in honour of the LGBT community, PinkNews.co.uk exclusively revealed last week.
Mr Tatchell told PinkNews.co.uk: "It's no big deal I haven't been invited. I'm not kicking up a fuss but it is odd that I've never been invited to a Downing Street reception despite my 40-plus years of campaigning for LGBT human rights.
"I'll just carry on campaigning. Although I've got my criticisms of both the Conservatives and Lib Dems, I'm happy to work with them for LGBT rights.
Mr Tatchell said he had "no idea whatsoever" why he had not been invited, adding that he had been "liaising" with Tory MPs and ministers since the election.
He said he would "probably" go if invited and said he would attend the event in the same manner as any other guest, rather than bringing banners and loudspeakers.
Downing Street have refused to reveal the guestlist for the event, although a spokesman said last week it was not based on political allegiances.
Mr Tatchell also said he believed Cameron's promises on gay rights had been "commendable" and the coalition government was "nowhere near as bad as some predicted".
He said his main concern was the legalisation of full civil marriage for gay couples.
Source: Pink News