Labour has pressed ministers over George Osborne's new role at the London Evening Standard, insisting new business appointments should not be announced before they have been considered by the Government's advisory committee.
Shadow Cabinet Office minister Andrew Gwynne said former ministers must get advice from the Advisory Committee on Business Appointments (Acoba) before announcing any new appointment, according to the ministerial code.
This followed an urgent question in the Commons on Monday as Mr Gwynne quizzed ministers on Mr Osborne's appointment as editor of the newspaper.
Speaking during Cabinet Office questions, Mr Gwynne said: "The ministerial code clearly states that former ministers require advice from Acoba prior to announcing any new business appointment, and Acoba is unable to report on their advice retrospectively after a new post has been made public.
"Can the minister explain why he gave different advice to the House during his response to the urgent question on Monday?
"Was it just a mistake, or had the rules conveniently been changed in the space of a week?"
Cabinet Office minister Ben Gummer said: "I think he has made his point very, very clear.
"Acoba are coming to their determination, they will consider all the evidence in the round, and it's important they do so without me prejudicing their decision by passing comment on it before they make their decision."
Labour MP Tom Blenkinsop (Middlesbrough South and East Cleveland) put further pressure on culture minister Matt Hancock over his relationship with Mr Osborne.
Labour deputy leader Tom Watson has said Mr Osborne would be expected to seek to influence ministers on media policy in his new role, and Mr Hancock should recuse himself from any matters relating to the Evening Standard, or ask to be moved to another Government department.
Mr Blenkinsop asked: "Will the minister for digital culture (Mr Hancock) recuse himself from decisions on Government media policy, given his very close relationship to the new editor of the London Evening Standard?"
Mr Gummer responded: "The minister is a decent and honourable man and he will make his own decision about his ministerial responsibilities.
"I think it's wrong to impugn his motives in the House, if I may say so."