Thanet MP Craig Mackinlay has reportedly been questioned by police about his election expenses.
It is understood the Tory was interviewed under caution for six hours following allegations of overspending in the 2015 election campaign which saw him come out on top after a bitter fight with Ukip leader Nigel Farage.
Kent Police did not mention Mr Mackinlay, a former Medway councillor, by name but said: “Investigation into this complex matter is ongoing and officers continue to follow lines of enquiry.
“Therefore it would not be appropriate to comment further.
“Officers from Kent Police continue to work with the Electoral Commission as the investigation continues.”
Reports in the media suggest police are due to meet the Crown Prosecution Service next Tuesday to discuss the matter.
It is part of a bigger investigation in which 24 MPs are understood to be under police investigation over claims they over-spent in their 2015 general election campaigns.
That probe centres on spending for a battle bus which was sent to key seats.