Clacton MP Douglas Carswell has said he will stand down as an MP and then stand for Ukip in the resulting by-election following his defection from the Tories.
He today announced that he would be leaving the Conservative Party, claiming the party's leadership are "not serious" about the change the UK needs.
If successful, Mr Carswell would become the eurosceptic party's only Westminster MP.
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PM spokesman's comments come following reports that the EU is secretly drawing up plans for greater military cooperation across the EU.
The Labour politicians put their alleged differences aside to jointly highlight how remaining in the EU could help fight climate change.
Late sunshine here and there this evening - but more cloud for southern Scotland, northern England and Northern Ireland again.