Ms Hernandez faces allegations she failed to properly declare election expenses when employed as the election agent for Conservative MP Kevin Foster.

Since she was elected on May 5, she has faced questions over her role in the financing of Tory campaigning but has insisted she has yet to be questioned or even contacted.

Now, the Independent Police Complaints Commission (IPCC) has confirmed a joint inquiry with a neighbouring force will take place to ensure independence for Devon and Cornwall police.

It said a managed investigation will be undertaken by West Mercia Police under the direction and control of the IPCC, and overseen by its deputy chair Sarah Green.

The probe will form part of a “wider investigation being undertaken by Devon and Cornwall Police” the IPCC added, in reference to separate allegations relating to other MPs implicated.

Deputy Chair Sarah Green said: “As Ms Hernandez is now a Police and Crime Commissioner, the IPCC will manage an investigation looking at whether she properly declared election expenses whilst acting as an election agent during the 2015 General Election.

On completion of the investigation we will decide whether any matters should be referred to the Crown Prosecution Service for its consideration.”

The inquiry will look into claims that more than two dozen Tory MPs failed to declare the costs of “battle buses” and hotel bills during last year’s General Election campaign.

The accused Devon and Cornwall MPs are Scott Mann in North Cornwall, George Eustice in Camborne and Redruth, Oliver Colvile in Plymouth Sutton and Devonport and Kevin Foster in Torbay.

Devon and Cornwall Police later announced that the investigation would be transferred to another police force.

The Office of the Police and Crime Commissioner (OPCC) made a referral to the Independent Police Complaints Commission (IPCC) immediately after the PCC election.

Andrew White, OPCC chief executive, said arrangements had 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.

Ms Hernandez, who was summoned to an emergency meeting by the Police and Crime Panel amid anger over her comments on the issue, has faced calls to step aside.

The panel warned her not to make any more “political statements”.

Exeter’s Labour MP Ben Bradshaw and former Lib Dem MP for Torbay Adrian Sanders have added to calls for Ms Hernandez to step aside.