Labour will attempt to force a Commons vote after changes to the ministerial code, accusing Boris Johnson of “trampling all over” long-standing principles.
It follows accusations the prime minister had watered down the rules for ministers after the code was amended to make clear they will not automatically lose their jobs for a breach.
A government policy document – published on Friday by the Cabinet Office – said it would be “disproportionate” to require ministers’ resignations for “any breach, however minor”.
Instead, sanctions could involve “some form of public apology, remedial action or removal of ministerial salary for a period”, it added.
But with the prime minister facing a Commons inquiry over whether he deliberately misled parliament over the Partygate scandal, opposition parties said Mr Johnson was “watering down the rules to save his own skin”.
The new code, however, continues to state that ministers “who knowingly mislead parliament will be expected to offer their resignation”.
When Parliament returns from week-long recess break, Labour said it will use an opposition day debate to ask MPs “to enshrine the commitment that ministers who commit serious breaches of the ministerial code will have to resign”.
“This cannot solely apply to misleading the House,” the party added.
The changes on Friday also made clear the prime minister has rejected a demand for his independent ethics adviser, Christopher Geidt, to be given powers to launch his own investigations into ministerial misconduct without seeking permission from Downing Street.
Angela Rayner, Labour’s deputy leader, said: “Boris Johnson is behaving like a tin pot despot and is trampling all over the principles in public life.
“Many decent Conservative MPs are deeply uncomfortable with Johnson’s behaviour and they now have the chance to stop his sinister attempts at watering down standards and integrity in our democracy.”
“Serious breaches of the ministerial code must result in resignation, whether they are deliberately misleading Parliament, bullying staff, bribery or sexual assault,” she added.
“This prime minister simply cannot be trusted to uphold standards in government while his conduct sinks further into the gutter and he gives the green light to corruption.”
However, speaking on Friday, Tim Durrant, an expert at the Institute for Government, said that the option of a more lenient penalty has always been available to prime ministers, at the cost of public controversy.
“There has been a public expectation that a breach always results in resignation,” he told The Independent.
“But the code itself has only ever explicitly included that sanction for ministers who have knowingly misled parliament. This update makes explicit that there are other sanctions available for different breaches, which was not previously stated. At the end of the day, it is always going to be the prime minister who decides who is in his or her government.”
Earlier, Chris Bryant, the chairman of the Commons Standards Committee, told BBC Radio 4’s Today programme the move on Friday demonstrated why an independent process was required when it came to judging possible ministerial wrongdoing.
The Labour MP, who has recused himself from chairing the Privileges Committee investigation into whether Mr Johnson misled parliament with his partygate reassurances, said the current system means “it still all lies in the prime minister’s hands and we know that the prime minister always finds himself innocent in the court of his own opinion”.
A No 10 spokesperson said: “The prime minister expects all ministers to maintain high standards of behaviour and to behave in a way that upholds the highest standards of propriety.
“He carefully considered and agreed the final recommendations on sanctions from the Committee in Standards in Public Life and the independent advisor on ministerial interests made in April 2021, which are now reflected in the ministerial code.”
They added: “They said it is entirely reasonable and fair to have a range of sanctions for any breach – in the same way the House of Commons standards process has a range of sanctions.
“The new code also has increased the powers and status of the independent adviser on ministerial interests and the requirements on high standards and principles of public life are unchanged.”
