A Conservative MP has been interviewed under caution over his election expenses, the BBC understands.
Craig Mackinlay, the MP for South Thanet, is being investigated over alleged overspending in the 2015 general election campaign.
Mr Mackinlay defeated the then UKIP leader Nigel Farage in the ballot.
Karl McCartney, whose bid to retain his Lincoln seat is also being probed, says a draft report into the controversy has been withheld by Tory central office.
Seventeen police forces across the country are looking into whether some MPs’ agents should have filed costs associated with battle bus visits to their constituencies in their local expenses.
The Tories said 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.
MPs ‘cast adrift’
Mr McCartney has accused Conservative Central Office (CCHQ) of keeping back from MPs a draft report from the Electoral Commission on the investigation.
In an email leaked to Sky News, he wrote to the party chairman, Patrick McLoughlin saying MPs felt “completely cast adrift” and “left to fend for themselves”.
The message continued: “We didn’t create this mess, the clever dicks at CCHQ did, and I don’t see their professional reputations being trashed in the media much.”
In a statement Mr McCartney said: “The Conservative Party advised us that the so-called campaign ‘battle buses’ were, as at previous general elections and in keeping with the practice of both the Labour Party and Liberal Democrats, a national campaign expense.
“This meant that they were not to be declared in our own election expenses.”
The office of Craig Mackinlay, who was questioned on Saturday, said it would not be commenting.
The Tories have blamed an “administrative error” for not declaring £38,000 of expenses for their Battlebus tour.
It follows a Channel 4 investigation into spending in key constituencies.
In June, Kent Police were given a further 12 months to investigate the claims of improper spending.
Granting the extension, District Judge Justin Barron described the allegations as “far-reaching”.
The inquiry, he said, could lead to election results “being declared void.”
MP Craig Mackinlay quizzed over election expenses}