Former chancellor George Osborne "disrespected" Parliament by accepting the post of editor of the London Evening Standard without first clearing it with the official watchdog, MPs have said.
The Commons Public Administration and Constitutional Affairs Committee said he had set an "unhelpful example" in taking the job without waiting for the advice of the Advisory Committee on Business Appointments (Acoba), which vets jobs taken by ex-ministers and senior officials.
In a highly critical report, the committee said Acoba had become a "toothless regulator" and that unless it was given statutory powers of redress the system would be remain open to "similar abuses" in future.
Mr Osborne, who has said he will not stand again at the general election on June 8, had been widely criticised for taking on the Evening Standard job while still sitting as the MP for Tatton in Cheshire.
The committee said: "We disapprove of the announcement of Mr Osborne's appointment as editor of the Evening Standard without waiting for Acoba's advice.
"This demonstrates disrespect for Acoba and for the business appointment rules and sets an unhelpful example to others in public life who may be tempted to do the same."
The committee - which had invited Mr Osborne to give evidence before the election was called - also highlighted his appointment as a part-time adviser to the US investment giant BlackRock, working one day a week for £650,000 a year.
It noted that prior to joining the company, Mr Osborne's 2014 Budget announcement allowing savers to cash in their pension pots had been warmly welcomed by BlackRock president Robert Kapito who said it was 25 billion dollars (£19.5 billion) a year of "money in motion".
The committee said it could not make any judgment on Mr Osborne's personal conduct as it had not taken evidence from him.
It added, however: "The only justification for a minister or civil servant taking public or private sector employment in a field for which they had responsibility is where they might be returning to or continuing to work in an occupation or profession where they already had an established track record and experience."
In other cases, the committee noted Mr Osborne's special adviser at the Treasury, Rupert Harrison, had also joined BlackRock while Liberal Democrat former energy secretary Sir Ed Davey was an adviser to the lobbying firm which acted for the French energy giant, EDF, in its successful bid to build the Hinkley Point C power station Sir Ed - who is standing in June to regain his seat of Kingston and Surbiton which he lost to Conservative James Berry at the 2015 general election - was responsible for awarding the contract when he was in office.
The committee said such cases underlined the need for a major overhaul of the Acoba system which is intended to prevent conflicts of interest when ex-ministers and senior civil servants take up private sector jobs within two years of leaving office.
"The failures of governments in this regard have damaged public trust in politics and public institutions and led to repeated scandals," it said.
"Acoba in its current form is a toothless regulator which has failed to change the environment around business appointments."