An annual windfall worth hundreds of thousands of pounds of public money is at the heart of a row about the future of the party’s sole MP Douglas Carswell.

Mr Carswell’s future is in doubt after former Ukip leader Nigel Farage and other senior Ukip figures called on him to quit over claims that he tried to deny Mr Farage a knighthood.

Paul Nuttall, the Ukip leader, has now ordered a formal investigation into the row that could end in his membership of the party being cancelled.

Ukip is entitled to the cash to fund its work because it won the support of more than 150,000 voters at the last general election and have more than one MP in the House of Commons.

Other MPs have traditionally passed this cash onto their political parties to help fund their parliamentary work.

However, Mr Carswell has refused to do so and has instead used the money to fund the work of Ukip’s Parliamentary research unit.

Mr Carswell is entitled to receive £217,000 to fund Ukip’s parliamentary work in the current financial year, figures show. Last year Mr Carswell claimed less than half of the £619,000 Ukip was entitled to.