Conservative MP Craig Mackinlay was questioned by Police under caution last week over his election expenses, the Telegraph can reveal.
The South Thanet MP reportedly spent six hours being interviewed by officers over alleged overspending in the 2015 election campaign in which he beat Nigel Farage and Al Murray, the Pub Landlord.
Kent Police are expected to meet with the Crown Prosecution Service next week to discuss a possible prosecution, it is understood, after the force concluded a series of interviews with Conservative staff and politicians about the alleged overspend.
Both Mr McKinlay and his agent Nathan Gray have denied any wrongdoing.
The Electoral Commission opened an investigation into election spending in the constituency last year after a journalist at Channel 4 News made allegations about the spending on hotels for activists campaigning in the seat.
It has been claimed that hotel and transport costs may have been recorded as national expenses rather than local in a bid to keep spending under strict caps.
The Commission has the power to impose a £20,000 fine if the rules have been breached.
Over the weekend former Conservative party chairman Grant Shapps claimed one of the Prime Minister's closest aides, Nick Timothy, "orchestrated" the campaign.
He told The Sunday Times: "I remember discovering partway through the campaign, I think, that Timothy was actually down full-time in Thanet.
“The wider issue is, were election expenses bust, and you can’t hire a hotel without applying any of that to local expenditure.
“And it just happens that Nick seems to have been orchestrating a lot of the activity down there, and he’s definitely front and centre of it, unfortunately from his point of view.”
A party source denied the claims.
There is bad blood between Mr Shapps and Mr Timothy after the former chairman allegedly blocked the adviser's bid to become an MP.
Kent Police's inquiries focus on whether election spending caps were breached during the bitter battle for the seat.
Officers would not comment on Mr Mackinlay's interview but said in a statement: "The Kent Police investigation into this complex matter is ongoing and officers continue to follow lines of inquiry.
"Therefore it would not be appropriate to comment further. Officers from Kent Police continue to work with the Electoral Commission as the investigation continues."
Mr Mackinlay's office declined to comment, but a source close to the MP confirmed he was interviewed under caution as part of the investigation on Friday last week.
A Tory source said: "They really put him through the mill, he was there for six hours."