Mr Johnson, who defeated Ken Livingstone in 2008, was previously rumoured to be planning to make the announcement at the State of London debate earlier this year.
When that announcement failed to materialise senior Johnson administration figures denied the plan and insisted the Mayor would “take time to decide over the summer” whether he would seek a second term.
Talking to LBC’s Nick Ferrari this morning Mr Johnson said he’d wanted time to “take a view on whether things were going broadly well” before deciding to run again.
More recently it’s been reported that the Mayor, widely seen as the Conservative’s best chance of keeping control of City Hall, has been using his decision whether to seek a second term as a bargaining chip in negotiations with central government over funding for London projects such as Crossrail and “vital” Tube upgrades.
Mr Johnson has also this morning attacked Government cuts, echoing comments made in May when he promised to mount a “Stalingrad-like defence” of the capital in negotiations with Ministers.
In a statement issued by his campaign team Mr Johnson said he was “fully focused on the job of Mayor not on campaigning.”
“Over the coming months we will be building our campaign team which I expect to include many who helped me last time. My focus, however, remains on delivering on the issues which concern Londoners – they come first and foremost.”
In 2008 Mr Johnson vowed not to seek more than two terms as Mayor, with Labour widely expected to adopt Ken Livingstone later this month as their 2012 Mayoral candidate the stage looks set for a contest between two candidates likely to hold office for just a further single term.
Mr Livingstone is being challenged for Labour’s nomination by former MP Oona King. The Labour party will announce the result of their ballot on September 24th.
