He will be called to give an oral statement and be questioned by the Standards and Privileges Committee at the Commons on 14 October, two weeks before the House returns from its summer break.
But Mr Hamilton will be required to take the rare step of swearing an oath before being cross-examined by the committee. Yesterday's decision by the committee, which had hoped to complete its inquiries quickly, means the saga will drag on into the autumn.
It is thought Mr Hamilton will be only the second MP to take the oath when giving evidence to a Commons select committee.
The first was the former Tory minister Andrew Mitchell when earlier this year he gave evidence to the old standards committee over his role in an early investigation into sleaze claims. Mr Mitchell lost his Gedling seat at the general election.
The committee's decision came after a two-and-a-half hour meeting in the Commons, for which MPs were recalled from their summer break.
It is considering the report of Parliamentary Standards Commissioner, Sir Gordon Downey, which was published last month.
Sir Gordon found "compelling" evidence that Mr Hamilton accepted cash payments from Harrods boss Mohamed al-Fayed in return for lobbying services.