A dozen police forces have passed files to the Crown Prosecution Service over allegations that up to 20 Conservative MPs broke local spending limits at the last general election.
Prosecutors have to decide whether to charge the MPs or their agents, after a 10-month investigation into whether party spending on an election battlebus that brought activists to marginal seats was wrongly recorded as national spending.
Downing Street refused on Wednesday night to comment on the development, but senior party figures are concerned that any successful prosecutions of sitting MPs could lead to election results being declared void, causing a string of byelections as the Brexit negotiations draw to a conclusion in late 2018 or early 2019.
Police have not named the Conservative MPs or agents under investigation, but it emerged on Tuesday that Craig Mackinlay, the Tory MP for South Thanet, was interviewed under caution over spending returns related to his electoral battle against the Ukip leader, Nigel Farage.
The revelations rounded off arguably the worst day in Theresa May’s eight-month stint as prime minister, after a Tory rebellion forced her chancellor, Philip Hammond, to drop his plan to raise national insurance for the self-employed only a week after it was announced at the budget.
There was even speculation in Westminster that May would consider seeking an early general election to draw a line under the spending allegations about the 2015 election.
A Conservative spokesman said: “We are cooperating with the ongoing investigations.”
Mackinlay did not reply to a request for comment but has previously said his returns were “lawful and proper”.
Under election laws, candidates for any party can only spend a set amount, typically about £15,000, on their campaign in a constituency. The exact sum is calculated on a per capita basis. Parties are allowed to spend more on nationwide campaigning using separate budgets.
The Scottish National party called on the Conservatives to “come clean” about who authorised spending decisions at the 2015 election and suggested the party may have “fraudulently won with a coordinated breach of electoral legislation”.
Pete Wishart, a senior SNP MP, said: “This expenditure was passed off as national expenditure, even though this activity was specifically targeted to support individual candidates.
“The Conservative central office now must tell us who signed off this expenditure, who authorised it and what advice was given about candidate expenditure.
“These are very serious allegations and the penalties for those guilty of election fraud could result in large fines and even imprisonment.”
Warwickshire police also said they had interviewed two people as part of their investigation, and a decision would be made soon about whether to hand the file to the Crown Prosecution Service (CPS).
Prosecutors have already received files from 12 police forces – in Avon and Somerset, Cumbria, Derbyshire, Devon and Cornwall, Gloucestershire, Greater Manchester, Lincolnshire, London, Northamptonshire, Nottinghamshire, Staffordshire and West Yorkshire.
Earlier on Wednesday, Will Quince, the Tory MP for Colchester, also revealed he had been interviewed under caution over allegations about overspending at the 2015 election. He said police told him there would be no further action against him after the interview, which took place in January.
The Morecambe and Lunesdale MP, David Morris, said he was one of the MPs to have been interviewed by police.
“Lancashire police interviewed me and they saw fit not to take it any further,” he said. He said he had not wanted a visit from the battlebus campaign at the centre of many of the claims about election spending breaches.
Morris told BBC’s Newsnight: “We were all given an email. Every one of us had the same email from Mark Clarke at the time, who was running the battlebus project, saying it was a national spend.”
He added: “I honestly believe not one MP is guilty of anything.”
Morris said his case was straightforward. “We did not want the battlebus, and that was said from day one. We got the battlebus, we were instructed to have the battlebus, which is the same for everybody else, which is what the parties do.”
A separate Electoral Commission inquiry into whether the national party broke election spending limits is also under way and is expected to come to a head soon, potentially within days.
The allegation, first uncovered by the Daily Mirror, is that spending in marginal seats on a battlebus tour was wrongly recorded as national spending, rather than local, to help specific candidates win against their Labour, Liberal Democrat or Ukip opponents.
Channel 4 also revealed separate allegations concerning South Thanet, showing that the hotel expenses of a team of Conservative party officials, including Nick Timothy, who is now May’s chief of staff, had been recorded as national rather than local.
Emails obtained by the broadcaster suggest two of May’s other aides, Stephen Parkinson and Chris Brannigan, were closely involved in Mackinlay’s campaign but expenses relating to their efforts were not recorded as local spending.
Mackinlay held off Farage by 2,812 votes in the closely fought seat, declaring spending of £15,016, slightly below the limit of £16,000.
But receipts for national Conservative party spending show that £18,000 was spent on accommodation for party workers in the Royal Harbour hotel in Ramsgate, in the South Thanet constituency, and a Premier Inn in Margate, which is just outside it.
A further £715 was spent on the Alpha hostel, used to accommodate a busload of activists who took part in a Stop Farage campaign.
Adding to pressure on May, the party is facing a mutiny from Conservative MPs under investigation who feel they have been hung out to dry by the party, which organised the battlebus campaign centrally.
One MP, who said he did not know whether the police investigation against him was still live, said it had been a “terrible year with this hanging over us and no support at all from CCHQ”.
In a leaked email to Patrick McLoughlin, the party chairman, Karl McCartney, the MP for Lincoln, complained that he and other MPs felt “completely cast adrift” and had been “left to fend for themselves”.
In a statement, McCartney said he had made clear his “forthright views” privately to a number of senior party figures on behalf of backbenchers.
Quince, who is not facing charges, said he considered the allegation to have been “vexatious and politically motivated”.
He added: “Politics is not a game. I would ask those individuals to think about the cost of this investigation, the important work those police officers could have instead been doing over this lengthy period, the stress that it put me, my family and my team under and the reputational damage to me personally.”
