The Conservative leader has now listed the benefit in the Register of Members' Interests, but only after a Labour MP lodged a complaint. The entry says he had free use of the gym at 194, Albert Embankment, the luxury apartment block where Lord Archer has a penthouse from January 1998 until November 1999.
He stopped using the gym after Lord Archer was forced to withdraw from the race to be London Mayor. It is likely Mr Hague was advised he should register his free access to the gym, which he shared with his aide Sebastian Coe.
Earlier this year Peter Mandelson registered his pounds 373,000 loan from Geoffrey Robinson after taking similar advice from the standards commissioner, Elizabeth Filkin, in the face of a complaint.
But though Mr Hague has registered the gift Ms Filkin will still complete her inquiry and pass a report to the House of Commons Standards and Privileges Committee.
Use of a commercial gym in Central London costs around pounds 1,000 per year. MPs are required to register any gift or other benefit which in any way relates to their membership of the house and which is worth more than 0.5 per cent of their salary, around pounds 225 per year.
"Both the possible motive of the giver and the use to which the gift is put have to be considered ... if there is any doubt it should be registered," the rules say.
When Mr Hague was using of Lord Archer's gym without registering it, he endorsed the peer's campaign to become Mayor of London. "This candidate is a candidate of probity and integrity," he said at the Conservative Party conference in October, after Lord Archer beat Steven Norris to the Tory nomination.
Fraser Kemp, Labour MP for Houghton and Washington East, complained to Ms Filkin about the gift. "I am pleased the registrar has forced Mr Hague to register this," he said. "It was clearly a benefit he was receiving in his role as leader of the opposition, and he should have registered it before. This facility was worth thousands which should have been declared."
Lord Archer's neighbours told a newspaper they were unable to use the gym for up to two and a half hours each morning while Mr Hague worked out with Mr Coe. Equipment had been moved so they could lay out a mat for practising martial arts, the neighbours said.
A Conservative spokesman declined to comment.Reuse content