Devon and Cornwall Police has said it will hand the investigation of alleged electoral fraud by the Conservative Party over to another force.

The police were called on to investigate whether the party had committed fraud by failing to disclose expenses related to its election battle bus in constituencies including Camborne and Redruth, where Tory MP George Eustice was re-elected, and North Cornwall where Scott Mann won the seat for the party.

The newly elected Police and Crime Commissioner, Alison Hernandez, has also been caught up in the scandal, as last year she was the election agent Torbay MP Kevin Foster, and signed the campaign's spending return which did not include the expenses.

Devon and Cornwall's Chief Constable, Shaun Sawyer, said: "Following a programme aired by Channel 4 on 20 and 21 April, the force received allegations relating to improper electoral campaign spending returns in Devon and Cornwall in the 2015 general election.

"I have decided that all allegations, irrespective of any constituency or any individual, within Devon and Cornwall will be transferred to another force. I am therefore currently in discussion with other forces in respect of this.

"I have also spoken with the chief executive of the Office of the Police and Crime Commissioner for Devon and Cornwall Police who is also making arrangements in respect of the PCC-elect Alison Hernandez in order that any matters relating to her may also be transferred to another force.

"It is imperative that the public and my workforce have confidence in this force in respect of transparency, integrity and impartiality in this matter."

Ms Hernandez said she had not been approached by the police about the matter, but stood ready to assist in any investigation.

She said: "I welcome the decision by Devon and Cornwall Police to transfer this matter to another police force. The transfer removes any suggestion that I could ever influence police action.

"This issue has been reported for many weeks in the media. Clearly, the people of Devon and Cornwall did not let it affect their vote. They have had faith in me to do this job so I intending to get on with it and not be distracted with other matters."

Office of the PCC chief executive Andrew White said the investigation would be transferred to another force with Assistant Chief Constable Paul Netherton acting as a liaison.

He said: "These arrangements have been put in place to protect Devon and Cornwall Police from any suggestions that they may be subject to undue influence, and to ensure that any individuals who form part of this investigation will be treated impartially by an independent police force."

The battle bus was funded by the central Conservative Party to ship activists to key constituencies, but constituency offices failed to include a total of £38,201 in hotel costs, which could have pushed them over spending limits.

Eight police forces are currently investigating, including applying for an extension to a one-year limit to bring prosecutions in such a case.

Anyone convicted in the investigation could face up to a year in prison, an unlimited fine, and be barred for three years from holding elected office, including serving as an MP.