Boris Johnson’s administration has received a double blow as Scottish Tory leader Ruth Davidson and a Lords whip quit their posts.
Ms Davidson said she had taken the decision to stand down as she wanted to concentrate her time on her young family.
But she also highlighted “the conflict I have felt over Brexit”, adding: “I have attempted to chart a course for our party which recognises and respects the referendum result, while seeking to maximise opportunities and mitigate risks for key Scottish businesses and sectors.”
Lord Young of Cookham, a Government whip in the upper house, was more direct, saying was “very unhappy” with the Prime Minister’s decision to prorogue Parliament for an extended period as the the October 31 deadline for Brexit looms.
The leading Brexiteer also hit back at Commons Speaker John Bercow’s criticism, saying it was “not constitutional” for the Speaker to intervene in such a way.
Mr Rees-Mogg insisted the prorogation move was not intended to limit the time available for MPs to debate Brexit but will allow the Government to tackle other issues.
He added: “Parliament wasn’t going to be sitting for most of this time anyway. This is completely constitutional and proper.”
On Mr Bercow’s intervention, Mr Rees-Mogg said: “It is not constitutional for the Speaker to express his opinion without the direction of the House.
“He has had no such direction and therefore his comments were in a private capacity. They can’t be as Mr Speaker.”
Mr Rees-Mogg led the Government’s defence of the prorogation as Labour and opposition parties vowed to press ahead with attempts to block a no-deal Brexit using legislation despite the decision to suspend Parliament for more than a month before the October 31 exit deadline.
Shadow international trade secretary Barry Gardiner said: “It is going to be extremely difficult. That’s why the Government is disingenuous to say this is not about trying to stop us doing that.
“We will be seeking measures on Monday to try and have what is known as a Standing Order Section 24 debate. We will seek to try and put through the appropriate legislation in this constrained timetable that the Government has now put before us.
Thousands of people rallied for hours outside Parliament on Wednesday night, and there were smaller demonstrations in other towns and cities as Remainers reacted to the prorogation announcement.
More than one million people have also signed a petition calling on Mr Johnson not to suspend Parliament.
Mr Johnson said on Wednesday that he wanted to prorogue Parliament in order to bring the current record-breaking session to a close in order to bring forward his Government’s new legislative agenda.
But former Tory prime minister Sir John Major was among those who attacked the move, saying he was seeking advice on its legality.