Twelve police forces have asked the Crown Prosecution Service to consider charges over general election expenses.
The CPS said it had received files from 11 forces, and a 12th, Staffordshire Police, confirmed to the BBC it too had sent one.
The files are for the CPS to decide whether charges should be brought.
It comes after complaints about the way Conservative “battle bus” visits to constituencies had been recorded in campaign spending returns.
The allegations came to light following an investigation by Channel 4 News into claims the Tories may have broken election law at the 2015 general election and three earlier by-elections.
The CPS confirmed files had been received from:
- Avon and Somerset
- Devon and Cornwall
- Greater Manchester
- West Yorkshire
On Monday, it was revealed that Craig Mackinlay, the MP for South Thanet in Kent, had been interviewed under caution over his election expenses.
Kent Police is not one of the forces to have sent a file to the CPS.
A second Conservative MP, Will Quince, who represents Colchester, said he had been told by Essex Police he faced no further action after voluntarily attending an interview under caution last January.
In a statement posted on Twitter, Mr Quince welcomed the decision by the police but said the complaint against him had been “vexatious and politically motivated”.
Police forces pass election spending files to CPS}