Justice Secretary David Gauke has resigned from government after it was announced that Boris Johnson will become the next Prime Minister.
He made his intentions clear over the weekend that a Johnson victory in the Tory leadership contest would lead to his departure, saying he was not prepared to condone a no-deal Brexit.
In a tweet following the announcement, the MP for South West Hertfordshire congratulated Mr Johnson and said he was "looking forward to returning to the backbenches."
The education minister Anne Milton has announced her resignation, citing "grave concerns" about a no-deal Brexit.
Posting her resignation letter on Twitter, the Conservative MP for Guildford said she regretted "very much" that the original March 29 Brexit deadline had not been met.
"I have always believed our departure from the European Union should be centred around future cooperation, and I had sincerely hoped that we would have been able to leave the EU in March with a deal in place," she wrote.
"I have grave concerns about leaving the EU without a deal and so I feel it is time for me to return to the backbenches."
She continued: "This has not been an easy decision to make, but I believe strongly that Parliament should continue to play a central role in approving a deal, and that we must leave the EU in a responsible manner."
Ms Milton has been the education minister since June 2017.
Rory Stewart confirmed his resignation as International Development Secretary in a tweet this morning, citing differences with Boris Johnson on Brexit and the suspending of Parliament as the reasons.
After the result was announced Mr Stewart posted a picture of himself with two horses and said he would be back to the backbenches tomorrow.
"Congratulations @BorisJohnson on becoming Leader. Honour to serve in turn as Minister of Environment @DefraGovUK, Mid East + Asia @DFID_UK, Africa @FCO, Prisons @MoJGovUK + then Development Secretary in Cabinet +NSC. Backbench tomorrow serving Cumbria. Thank you all. More walking!"