Speech comes on same day thousands protested for PM's resignation

Boris Johnson today declared June 24 would be known as ‘independence day’ as he delighted Tory activists at a gathering designed to demonstrate Tory loyalty.

The outgoing London Mayor could not resist a pro-Brexit jibe at the Conservative Spring Forum, intended as a springboard for the May local elections.

Prime Minister David Cameron hoped to use the event to draw a line under questions about his personal finances after a toxic week which culminated in calls for his resignation after he admitted to owning shares in his late father’s offshore investment fund until 2010.

Boris Johnson today declared June 24 would be known as ‘independence day’ as he delighted Tory activists at a gathering designed to demonstrate Tory loyalty

The Conservative Party is wrestling to maintain a show of loyalty ahead of local, devolved and mayoral elections on May 5 despite deep splits over the June referendum on EU membership.

Mr Johnson used his speech to launch a spirited attack on the ‘extreme left’ backing Sadiq Khan to reclaim London’s City Hall.

But he quipped: ‘London is a city of 400,000 French men and women, which will remain the case… our talented will remain the case after June 24 - or independence day as I’m sure it will be known.’

Mr Johnson used his speech to launch a spirited attack on the ‘extreme left’ backing Sadiq Khan to reclaim London’s City Hall

Mr Cameron later insisted he would not be addressing the EU question in his local election launch at the conference.

But he drew laughs from activists when he suggested Mr Johnson had done the same.

The Prime Minister said: ‘Boris and I agreed we weren’t going to talk about Europe - did Boris meet his promise? I think he did - yes? No?

‘I will just say one thing about Europe - I think it’s something we can all agree about.

Mr Johnson infuriated the Prime Minister by declaring he would back Brexit in the referendum on June 23

‘Whatever side we are on in this debate, let us not forget why we are having this referendum.

‘We are having it because this party, this Government, made a promise to the British people, is keeping a promise to the British people, so after 40 years they get their say - Europe in or out.’

Mr Johnson infuriated the Prime Minister by declaring he would back Brexit in the referendum on June 23.