Calder Valley's Craig Whittaker, Colne Valley's Jason McCartney, York Outer's Julian Sturdy, and Scarborough and Whitby's Robert Goodwill all previously said Mr Cummings' should go after it was revealed he allegedly broke lockdown rules and travelled to Durham, with the trio all sticking to their guns today following Mr Cummings' explanation.
Shipley MP Philip Davies has joined them, saying: "It is admirable of the Prime Minister to be loyal to his staff and to seek to defend and support those who work for him. Dominic Cummings should now repay that loyalty to the Prime Minister by resigning his position for the good of the Prime Minister, the Government, and the country."
Alec Shelbrooke, MP for Elmet and Rothwell, confirmed to the BBC he believed Mr Cummings' could no longer stay in his job, while Brigg and Goole MP Andrew Percy told Sky News the same.
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Harrogate and Knaresborough's Andrew Jones had also indicated in an email to a constituent he thought Mr Cummings should resign but has yet confirmed whether he still holds the view after Mr Cummings' press conference at Downing Street yesterday.
In the appearance, Mr Cummings – Boris Johnson’s chief adviser – defended a 260-mile trip from London to the north-east of England he made with his family during lockdown, explaining that he believes he behaved “reasonably”.
However this morning Douglas Ross, the parliamentary under-secretary of state for Scotland, quit the Government, saying that he could not “in good faith” defend Mr Cummings’ actions.
It follows criticism from a string of Tory MPs, including veteran Sir Roger Gale who said that the Conservative backbench 1922 Committee should make it clear to Boris Johnson that Dominic Cummings should go.
“The time I think has come for Mr Cummings to resign or for the PM to dispense of his services,” Sir Roger said.
The North Thanet MP told the PA news agency: “There are people on the 1922 executive who are courageous, and that’s their job.
“They are elected to tell the PM what he needs to hear, not what he wants to hear.”
Senior Tory William Wragg said that it was “humiliating and degrading” to see ministers put out agreed lines in defence of Mr Cummings.
Mr Wragg, chairman of the Public Administration and Constitutional Affairs Committee in the Commons, said: “We cannot throw away valuable public and political good will any longer.
“It’s humiliating and degrading to their office to see ministers put out agreed lines in defence of an adviser.
“This is a time of national emergency and our focus must be unrelenting. We owe it to the nation.”
Tory MP Caroline Nokes, chairwoman of the Commons women and equalities committee, said she had informed her party whips there could not be “wriggle room” for some people when it comes to lockdown rules.
The former immigration minister tweeted: “I made my views clear to my whip yesterday. There cannot be one rule for most of us and wriggle room for others.
“My inbox is rammed with very angry constituents and I do not blame them. They have made difficult sacrifices over the course of the last nine weeks.”
But Downing Street declined to answer numerous queries that remain unresolved, including regarding a trip to Barnard Castle which Mr Cummings said was to test his eyesight.
Earlier Cabinet Office minister Michael Gove said the journey, some 25 miles from where the aide was isolating, was “completely appropriate” because he was “preparing to return to work” by checking he was safe to drive the long trip back to London.
“It’d have been entirely within his right to return to work that day on the basis of the advice he had been given, that’s my understanding, so that drive was completely appropriate,” Mr Gove told BBC Radio 4’s Today.
Former Greater Manchester Police chief constable Sir Peter Fahy said officers had become “frustrated” by the fiasco, which may hinder policing with the rules “now very confused”.
And he suggested that Mr Cummings’ trip to Barnard Castle “certainly appears to be against the Highway Code – it’s not the way to test your eyesight, and put potentially other people in danger”.
He also said “it may well be that absolutely he’d have been turned back” by officers if they stopped him during the drive north from London in March.
NHS Confederation chief executive Niall Dickson said: “Because of the way this story has unfolded, there is certainly concern among our members, health leaders, that it could damage staff and public confidence in official guidance.”
But the Prime Minister’s official spokesman said: “I can’t be a spokesman for special advisers, that’s not my job.
“If you have questions in that regard they’ll have to go elsewhere I’m afraid.
“The PM asked Dominic Cummings to set out his explanation in public and he did that last night, he answered questions extensively.”