The number of Conservative MPs who openly said they do not want to see Boris Johnson as the party leader and prime minister with the ongoing partygate effect has reached 28 on Tuesday.
Carlisle MP John Stevenson said in a statement that he has been "deeply disappointed" in the lockdown parties at the government offices.
He said he has urged Johnson to put himself forward for a vote of confidence but the prime minister appeared unwilling to do so.
“Sadly, the prime minister appears unwilling to bring matters to a head and submit himself to such a vote,” Stevenson said.
“Therefore, the only option is for the Conservative MPs to facilitate a vote of confidence. I have already taken the appropriate action.”
Earlier on Tuesday, Dame Andrea Leadsom, the former Cabinet minister, condemned Johnson’s "unacceptable failings of leadership" over the partygate affair.
Last week, Johnson repeated his apology over the parties that took place during the COVID-19 lockdown at Downing Street, after a report by a senior civil servant revealed more details about the gatherings.
“I am humbled and I have learnt a lesson,” Johnson said, adding that he took the full responsibility for the parties despite he was not aware of many of them, adding that he was “appalled” by some of the findings of the report compiled by Sue Gray.
He also told a group of reporters that he would not resign over the partygate and it should now be left behind to deal with the country's problems, including the cost of living crisis.
A total of 54 letters by Tory MPs are needed to be submitted to the party’s 1922 Committee to trigger a leadership vote.
Sir Graham Brady, the chair of the committee, is the only person to decide a vote of confidence if the threshold of 15% of Tory MPs asking for such a vote with letters is reached.
Met police investigated the COVID-19 rules breach during the lockdowns at Downing Street and issued 126 fines to 83 individuals, including Johnson.