Johnson said his agreement with the EU was an "oven-ready deal", a phrase he has repeated in recent days, that was "ready to go" as soon as parliament returns on December 13, the day after the election.
He also hit back at Donald Trump's comments, after the U.S. President said the Brexit deal might hinder a future trade agreement between the States and Britain.
He also said it was a matter of "deep regret" that the UK had not left the EU on October 31, as he had pledged it would.
But Jo Swinson, leader of one of the UK's opposition parties, said Johnson only had himself to blame.
"He wanted this job for so long and he was prepared to say whatever he felt he should say in order to get that job without giving any real thought to what he would do" said the Liberal Democrat leader.