The police probe into Conservative election expenses has deepened with the interviewing of a second Conservative MP.

Will Quince, the MP for Colchester, said he voluntarily attended an interview under caution last January, but had been told by Essex Police he faced no further action.

In a statement posted on his Twitter feed, Mr Quince welcomed the decision by the police but protested that the complaint against him had been “vexatious and politically motivated”.

The disclosure follows the revelation that Craig Mackinlay, who defeated Ukip leader Nigel Farage to hold South Thanet for the Tories, was questioned for six hours last week by Kent Police.

The investigation has sparked a Conservative civil war, with a third MP, Karl McCartney, protesting that a draft report into the controversy has been withheld by Tory central office.

Mr McCartney’s Lincoln seat is among those being investigated by 17 police forces, which are looking into whether costs associated with battlebus visits should have been filed within local expenses.

The Tories say they had been campaigning “across the country for the return of a Conservative government” and, as a result, associated costs were regarded as national not local expenditure

There are strict limits on local spending during an election campaign – and breaching them can be considered a criminal offence.

The so-called Battlebus 2015 tour saw Tory activists driven to 29 marginal seats in the days before the general election.