David Cameron will face Parliament today even though half his party is against him on the EU

Prime Minister David Cameron will explain to Parliament this afternoon why he wants Britain to stay in the EU. It's going to be very interesting to see the reception he gets from his own party, because so many of them have announced that they will be supporting the campaign for Britain to leave the EU.

At 3.30 pm Cameron will address the House of Commons for the first time since he announced that there will be a referendum on whether Britain should remain in 28-nation bloc on June 23. Cameron called the referendum after he managed to get all the EU's heads of state to agree to a deal that he claims will reform Britain's relationship with the EU.

The most high-profile Tory backing the leave campaign is Mayor of London Boris Johnson who called the referendum a "once-in-a-lifetime chance to vote for real change." It's a really big deal that Johnson has come out for leaving the EU, as a recent poll in the Evening Standard found one in three voters regard Johnson's opinion as "important" when it comes to deciding which way to vote.

As well as Johnson, six of Cameron's own cabinet ministers are backing the Leave campaign and according to political blog Guido Fawkes, around half of Tory MPs who have made up their mind will be opposing the Prime Minister as well.