Former cabinet minister Nadine Dorries said she was quitting with immediate effect in June but has yet to formally resign.
Nadine Dorries has come under fresh pressure to quit as an MP after failing to speak in the Commons for more than a year.
The former cabinet minister announced in June that she was resigning with “immediate effect” after she failed to receive a peerage in Boris Johnson’s resignation honours list.
But the Tory MP is yet to stand down formally, claiming she is investigating why she was refused a seat in the Lords.
Prime Minister Rishi Sunak has already said the former culture secretary’s voters “aren’t being properly represented”.
And now immigration minister Robert Jenrick has said it is time for her to quit.
“I think being a Member of Parliament is a special privilege. You sign up for a term in office,” he told Sky News.
“If you decide you want to leave Parliament for whatever reason, you need to get on and do that.
“I don’t think that Nadine Dorries’ constituents are being properly represented. I hope she’ll reach that conclusion soon.”
Ms Dorries remains as MP for Mid Bedfordshire but is hosting a weekly chat show on Talk TV and has written a book titled The Plot: The Political Assassination Of Boris Johnson, to be published in September, just days before the Conservative Party conference.
The Mid Bedfordshire seat has been held by Ms Dorries since 2005 and the Conservative Party generally since 1931.
Labour is hopeful of snatching the seat although the Liberal Democrats also believe they have the chance of springing another by-election shock.