Labour has demanded to know how many times Tory ministers have sent confidential government papers to their personal phones.
Home Secretary Suella Braverman has admitted she repeatedly used her own Gmail account for official business.
Rishi Sunak last week re-appointed the minister nicknamed “Leaky Sue” just six days after she was sacked for leaking sensitive immigration plans on her mobile.
Following a Home Office investigation, Mrs Braverman on Monday admitted she had forwarded official documents to her personal phone on six further occasions.
Keir Starmer on Monday instructed his frontbenchers to submit a blitz of requests demanding investigations into whether their opposite numbers in the Cabinet had also forwarded sensitive information to their own phones.
It is understood shadow ministers have put down a series of named day questions to government departments, which must be answered within three days.
It is a breach of the ministerial code for ministers to forward official documents to their personal mobiles.
Security guidelines state they should not use their own personal IT - including devices and email accounts - for Government business at any classification. Instead, Government systems should, as far as reasonably possible, be used.
The Prime Minister is under pressure over his decision to allow Mrs Braverman to return to the Home Office.
The Home Secretary on Monday said she is "sorry for the errors of judgment" after she was forced to make an extraordinary series of bombshell confessions about her carelessness with confidential government papers.
She admitted that it took her more than four hours to report a security breach when she accidentally emailed the wrong person with sensitive migration plans.
Mrs Braverman faced up in a letter to the chair of the Commons home affairs committee following an official probe into her conduct.
She revealed that she has been given a briefing by security experts on what constitutes appropriate use of Government and personal IT.
Labour’s Yvette Cooper last said neither Mr Sunak nor Mrs Braverman “recognise the gravity of these issues”.
The shadow home secretary added: “The Home Secretary has now admitted she sent government documents to her personal phone six times in 43 days - that’s once in every week she was in the post.
“Rishi Sunak was so irresponsible in reappointing her to her post.”
