MPs are trying to force Rishi Sunak to reveal whether civil servants raised security concerns about the home secretary.
The Lib Dems are proposing an amendment to the National Security Bill that would compel the prime minister to publish advice from the cabinet secretary.
Sunak’s early days in office were overshadowed by the row over his reappointment of Suella Braverman as home secretary just six days after she had to resign for breaching security rules.
She had shared a document with a Tory MP on the government’s immigration policy.
Braverman also accidentally sent a copy of the email to a parliamentary staff member.
It was then revealed she had sent government documents to her personal email address six times during her first stint as home secretary.
The Lib Dem amendment would require a memo to be published by the cabinet secretary - the most senior civil servant - about any advice given to the PM on the security implications of ministerial appointments.
They pointed to Braverman’s appointment, as well as that of Gavin Williamson and Dominic Raab, who have also come under fire in recent weeks.
Williamson resigned last week amid allegations of bullying and Raab has asked Sunak to launch a formal investigation into allegations he bullied civil servants.
The Lib Dems say these are examples of the prime minister’s poor judgement and the need for parliamentary scrutiny.
Conservative MPs, a number of whom raised concerns publicly about Braverman’s appointment, are being encouraged to back the amendment.
Lib Dem home affairs spokesperson Alistair Carmichael said: “At every turn we see a yawning gap between Sunak’s rhetoric and his actions.
“It is clear that the only way to put the national interest first under this prime minister is to embarrass him into doing the right thing. It is therefore essential that this amendment is passed.
“In a dangerous world, and with a prime minister who clearly prizes party management over professionalism, parliamentary scrutiny of appointments has never been more vital.”
The Lib Dems have tabled the amendment to the bill which is at its “report stage” in the Commons - one of the final stages before it moves to the Lords.
Voting on individual amendments at this stage are in the gift of the Speaker, Sir Lindsay Hoyle.
In her resignation letter to Truss, Braverman admitted sending an official government document from her personal phone.
“I have made a mistake, I accept responsibility; I resign,” she said.
She later revealed she apologised to Sunak when she was reappointed as home secretary after he entered No.10.
Braverman has since requested briefing and guidance by “security experts on what constitutes appropriate use of government and personal IT”.