Nigel Farage’s defeat at last year’s general election could be declared void after a judge said claims of overspending by his Tory opponents were “wholly exceptional”.

The UK Independence Party leader lost the race for Thanet South by less than 3,000 votes to Tory Craig Mackinlay in one of the most tightly fought battles of the election.

However allegations have since emerged that the Conservatives wrongly categorised spending as national rather than local, thereby not exceeding constituency spending limits.

The judge looking into the claims on Wednesday extended an investigation by another 12 months to find out the truth.