London, Jul 24 (IANS): Boris Johnson, who took over as Britain's 77th Prime Minister on Wednesday, said he wants to "change the country for the better" and that the "work begins now".

Johnson, who succeeds Theresa May, said the country would definitely leave the European Union on October 31.

"No ifs, no buts... The buck stops with me," he said, in his first speech as PM outside 10, Downing Street.

"The doubters, the doomsters, the gloomsters" who say Brexit cannot be done are "wrong", he added, reported the BBC.

Setting out his priorities, Johnson hit out at the "pessimists" who do not believe Brexit can be delivered.

In what is seen as an indirect attack at his predecessor, he called for an end to the "three years of unfounded self doubt" and "indecision".

"The time has come to act, to take decisions and change this country for the better," said Johnson, who was Foreign Secretary in May's cabinet, before quitting last year.

"Let's get going no... And yes, let's start now on those free trade deals. All this and more we can do now and only now at this extraordinary moment in our history," he added, reported CNN.