In a press conference outside his north London home on Sunday, Mayor and Member of Parliament Boris Johnson said he would campaign for the UK to leave the European Union in June's referendum.
Johnson said Prime Minister David Cameron had not achieved fundamental reform of the European Union: "I will be advocating Vote Leave ... because I want a better deal for the people of this country to save them money and to take back control."
Johnson joins six cabinet ministers who have gone against Cameron's position. A significant number of Conservative members of parliament are also believed to be campaigning for an exit from the EU.
The betting agency Ladbrokes has shortened the odds for Johnson to become the head of the Conservative Party:
According to the bookmaker, the odds of a British exit, or Brexit, from the European Union have improved and Johnson has become the favorite to lead the Conservative Party whenever Cameron decides to step down. Opinion polls show little margin between Brits who want to stay in the European Union and those who plan to vote to leave.
Political and financial pundits have called Johnson's announcement significant, with some suggesting that it could affect the value of the British pound.
Early Sunday, BBC radio news called on news outlets - including DW - to let them know where Johnson was, in what turned out to be a day of stage-managed presentations on the UK's membership in the European Union.
Prime Minister Cameron appeared on Sunday morning television and made an unusual, direct appeal to Johnson: "I would say to Boris what I say to everybody else which is we'll be safer, we'll be stronger, we'll be better off inside the EU."
"Yes, of course if Britain were to leave the EU that might give you a feeling of sovereignty but you've got to ask yourself: Is it real?" Cameron said. Leaving the EU would be a "leap in the dark," he added.
Johnson reportedly informed Cameron of his decision to back the Vote Leave campaign by text message a few minutes before he spoke on camera.
The six ministers who have come out in favor of leaving the EU include Justice Secretary Michael Gove - one of Cameron's closest friends and allies.
On Sunday, Scottish First Minister Nicola Sturgeon confirmed that she would support staying in the European Union. She said a successful vote to leave would "almost certainly" trigger a fresh independence referendum in Scotland.
jm/mkg (Reuters, AFP)