The EU Commission spokesperson added that Brussels was on a "Brexit break" and that it would also "refrain from any positions or opinions that would risk interfering with the ongoing leadership contest in the Conservative party". The campaigning between the two finalists could last for up to one month. Her replacement is due to be in place by the end of July.
Mr Johnson, a former foreign secretary in the Theresa May Cabinet, is seen as a frontrunner to take over as Conservative Party leader and Prime Minister. When the list is down to just two names the task will be handed over to grassroots members of the Conservative Party.
"This is my plan - one that can be delivered". The gaffe-prone politician voted for May's Brexit deal when it was put to parliament the third time.
Media captionDominic Raab: "I am the candidate who can be trusted to deliver on Brexit".
Now the party and the country may have a true Brexiteer at the helm.
The Brexit Secretary delivered a damning indictment on May's deal which he has suggested would lock the United Kingdom into the EU's orbit for years to come.
The European Parliament's chief Brexit negotiator, Guy Verhofstadt, also responded with something approaching alarm, tweeting: 'This would not only hurt the UK's credibility as an global partner but it is absolutely unacceptable and contradicts what nearly every lawyer in the United Kingdom thinks about it'. He has the most eye-catching background of any candidate: a sometime tutor to Princes William and Harry, Stewart once walked across Afghanistan and was deputy governor of a province in Iraq after the 2003 US-led invasion.
Hunt has held a variety of government posts and has been foreign secretary since Johnson resigned in JuIy over Brexit.
Mr. Johnson is expected to launch his campaign on Tuesday and so far he has kept a lower profile than the other candidates.
Hunt has aimed to pitch himself as a moderate who will accommodate Remainer concerns while delivering Brexit.
However, he could find, as May did, that trying to appease both sides eventually makes everyone unhappy.
Hunt's campaign is also supported by Amber Rudd, another Theresa May loyalist.
Gove, again one of his main rivals for the leadership, on Monday taunted Johnson.
Like Johnson, Gove helped lead the campaign to leave the European Union, but scuttled his friend Johnson's bid to become prime minister in 2016 when he unexpectedly withdrew support and chose to run for the job himself a move that gives him a lingering taint of treachery in the eyes of some Conservatives.
Taking a dig at Johnson's campaign, Gove said on Monday he would never use the taxation system to give the wealthy a tax cut.
Environment minister Michael Gove and former Brexit negotiator Dominic Raab also had fair odds.
Any future successful candidate will have to bring together a divided Conservative Party that has struggled to unite in the face of bitter divisions over the Withdrawal Agreement.
Conservative MPs who want to replace her must have the backing of eight other party colleagues to get to the next stage of the contest.
A future Prime Minister would have to show a full commitment to Brexit which could be a hard balancing act given that many Conservative parliamentarians are Remainers.