British MPs will hear why their Prime Minister believes they should remain in the EU when he speaks in the House of Commons this afternoon.

David Cameron was dealt a major blow yesterday after Boris Johnson said he will campaign to leave the union.

The London Mayor said one of his main concerns is about sovereignty.

These British people have mixed views on the topic:

Boris Johnson claims people should vote for "real change" after saying he'll campaign for Britain to LEAVE the EU - ahead of June's referendum.

His decision has been criticised by senior figures in the Conservative party in the UK, including Lord Heseltine.

The move also sets the London Mayor against his father Stanley - a former MEP and pro-European.