David Davis was right to resign from Theresa May’s Cabinet, Birmingham Conservative MP Andrew Mitchell said.
Mr Davis stood down as Brexit Secretary in protest against the Government’s planned deal with the EU.
But Mr Mitchell (Con Sutton Coldfield) said the Prime Minister needed a Brexit Secretary who supported the proposed deal.
He said: “I’m obviously very sad that David resigned.
“It is a principled resignation from a skilled and impressive politician.
“But I have no doubt he will be a powerful force within Parliament from now on. And it is of course Parliament that will ultimately make the key decisions.
“He was clearly right to resign because, as he himself said, whether the Prime Minister’s deal is right or wrong, she needs a Brexit Secretary who agrees with her.”
Mr Mitchell is a close friend of Mr Davis, but disagrees with him about Brexit and campaigned to remain in the European Union.
He said he did not oppose the Government’s planned Brexit deal.
Meriden MP Caroline Spelman (Con) backed the deal, saying: “I fully support what the Prime Minister is saying.”
Mr Davis quit in protest at the Government’s proposals for a deal with the EU . It was apparently agreed by the entire Cabinet – including Mr Davis – when they met last week.
His dramatic announcement came late on Sunday night.
In his resignation letter, he said he feared the Government would fail to keep its promises that the UK would leave the Customs Union and the Single Market.
Mr Davis said: “I am afraid that I think the current trend of policy and tactics is making that look less and less likely.”
He added: “The general direction of policy will leave us in at best a weak negotiating position, and possibly an inescapable one.”
And the Government’s negotiating approach was encouraging the EU to demand even more concessions, he claimed.
Mrs May appointed Dominic Raab, the former Housing Minister, as the new Brexit Secretary.
The resignation threatened to plunge Mrs May into a fresh leadership crisis. But Mr Davis said a leadership challenge would be the “wrong thing to do” and insisted he believed Mrs May was a “good prime minister”.
Asked by BBC Radio 4’s Today programme if she could survive, he replied: “Oh yes, of course.”
Leading Brexiteer Jacob Rees-Mogg said it will be “very difficult” for Mrs May’s Brexit plans to win MPs’ backing without Mr Davis.
He told BBC 5Live: “These proposals will have to come to the House of Commons in legislation and the question is ‘will they command support from Conservative MPs?’.
“And I think without David Davis there, without his imprimatur, it will be very difficult for them to get the support of Conservative MPs and therefore the Prime Minister would be well advised to reconsider them.”
He disputed a suggestion that Mrs May’s position was now untenable, saying: “Even the greatest of leaders can find that some of their proposals do not command widespread support and have to review them, even when they’ve got large majorities.”