Boris Johnson has been accused of a “clear breach” of the rules for not properly asking permission from an official watchdog to start a new job at the Daily Mail.
On Friday afternoon the newspaper confirmed the former prime minister would be writing a weekly column.
Former ministers who have left the government in the last two years must apply to the Advisory Committee on Business Appointments (Acoba) before accepting a new job.
But in a statement, Acoba said Johnson had only informed it 30 minutes before the Daily Mail announced the move, in a “clear breach” of the rules.
“The ministerial code states that ministers must ensure that no new appointments are announced, or taken up, before the Committee has been able to provide its advice,” it said.
“An application received 30 minutes before an appointment is announced is a clear breach.
“We have written to Mr Johnson for an explanation and will publish correspondence in due course, in line with our policy of transparency.”
The purpose of the rule is to avoid “any suspicion that an appointment might be a reward for past favours”.
It is also to stop the risk that an employer “might gain an improper advantage by appointing a former official who holds information about its competitors, or about impending government policy”.
Or the risk of a former minister “improperly exploiting privileged access to contacts in government”.
Johnson quit as an MP after learning the Commons privileges committee had found him guilty of lying to parliament over partygate.
MPs will vote on Monday whether to approve the committee’s report which said Johnson should have faced a 90-day suspension had he not already resigned.
The cross-party group also wants Johnson banned from holding a pass to access parliament.
The sanctions proposed by the Tory-majority committee are expected to pass, with only a relatively small group of Johnson loyalists set to oppose the report’s findings, although many more Conservatives could simply not turn up.