Two Tory MPs reveal CPS is reviewing their election spending

The allegation was made in June 2016 and at the time Essex Police made an application to the Electoral Commission for an extension to investigate.

The Crown Prosecution Service has received files from 12 police forces investigating allegations of general election expenses fraud.

However, he said that the inquiry has caused stress to his staff and family and he had suffered "reputational damage" while it was carried out.

"We need to make sure that all parties get that through the system and actually we have a fair and satisfactory conclusion which means that those MPs who did nothing wrong, whose election expenses are absolutely as the rest of ours were, are not tarnished".

The investigation has sparked a Conservative civil war, with a third MP, Karl McCartney, protesting that a draft report into the controversy has been withheld by Tory central office.

Particular attention was given to the Conservative Party's "BattleBus 2015" campaign, which saw activists bussed to 29 marginal constituencies in England, including Lincoln.

Pressure on Conservatives MPs intensified on Thursday after the Electoral Commission imposed a £70,000 fine on the Conservative party and referred its registered treasurer, Simon Day, to the police after finding numerous failures to declare spending on its election.

The Sun and the Telegraph both reported on Tuesday evening that Craig Mackinlay - who narrowly defeated the former UK Independence Party (UKIP) leader Nigel Farage in 2015 - was interviewed under caution by police for six hours last week.

Sky News understands the files relate to allegations against the Tories.

Staffordshire Police separately confirmed it had sent a file to prosecutors.

Theresa May was also confronted about the allegations for the first time in an interview with ITV.

CCHQ has always taken the view that its nationally directed battlebus campaign - a highly-publicised and visible activity with national branding - was part of its national return, and it would have no reason not to declare it as such, given that the Party was £2 million below the national spending threshold.

The Conservatives said they had accepted last March they had made "an administrative error".

'Moving on to the allegation itself, I consider this to have been vexatious and politically motivated, ' he said.

"Political parties of all colours have made reporting mistakes from time to time", a party spokesman said. "In fact there were some issues that the party itself raised with the Electoral Commission through their investigations", May said.

Seventeen police forces across the country are looking into whether some MPs' agents should have filed costs associated with battle bus visits to their constituencies in their local expenses.

  • Jon Douglas