Boris Johnson has "embarrassed" the UK internationally and would fail as Prime Minister, a west London MP has said.
The former London mayor today confirmed at a business event in Manchester that he would run in a Conservative Party leadership contest, saying, 'of course I'm going to go for it.'
It comes as Prime Minister Theresa May told senior MPs in the party she would resign once MPs back her Brexit deal.
At the 1922 Committee meeting, Mrs May told MPs she would agree a timetable for the election of a new leader after taking her Brexit deal to Parliament for a fourth time next month.
Labour's Ruth Cadbury dismissed Boris Johnson as her replacement, saying he had failed when given senior roles in politics.
The Brentford and Isleworth MP told ITV's The Late Debate: "I'm worried about the alternatives [to Theresa May].
"He was an embarrassment internationally to the UK when he was Foreign Secretary, and he was a pretty bad Mayor of London.
"There was the appalling Garden Bridge proposal where he wanted to favour his friends and cost Londoners a fortune."
Mr Johnson, currently the MP for Uxbridge and South Ruislip, was one of the front-runners to succeed David Cameron after he resigned as Prime Minster following the Brexit referendum in 2016.
However, he announced he would not be standing after close-ally Michael Gove questioned his leadership qualities.
Bob Neill, the Conservative MP for Bromley and Chislehurst, refused to back Mr Johnson in a leadership contest.
He said: "I don't think that comes as a complete surprise that he's going to run. There are many very good people, who I think will stand.
"We should wait until Theresa has formally announced her withdrawal. I want to see a candidate who makes sure we remain a pragmatic, progressive one-nation party.
"It's very important we have someone who actually give leadership, who doesn't drift off to the left as the Labour Party has done."
Mr Johnson resigned from Mrs May's Cabinet last year over the Government's handling of the Brexit negotiations.
Several senior Tories are expected to challenge of the leadership, with Prime Minister possibly stepping down early next month.
Lib Dem peer Meral Hussein-Ece said: "[Mr Johnson] would be dangerous in such a position.
"He's shown as Foreign Secretary, one of the senior positions of office in this country, that he was completely incompetent.
"There are all sots of things that Londoners really want to be tackled and because the Conservative Party is is so absorbed in leadership problems and their shambolic negotiations on a Brexit deal, nothing else is being done."