A dozen police forces have sent files to prosecutors as part of a probe into the Conservatives' 2015 election expenses as Tory MPs urged the party's leadership to take action on the issue.
With police and the Electoral Commission investigating, Conservative Party chairman Sir Patrick McLoughlin has been urged to act to protect MPs who face accusations they breached local campaign spending limits.
At least three Tory MPs have been quizzed by police investigating whether election finance laws were broken in the 2015 contest.
Tory MP Anne-Marie Trevelyan said she hoped the "very difficult" situation would be resolved "very quickly".
She said: "I think the whole situation is very difficult and I hope very much that it will be resolved this week.
"I understand from colleagues that we are into that stage and the party chairman will be doing all he can to make sure that the right outcome and that those MPs who did nothing wrong, they followed the appropriate electoral law, have this really difficult pressure taken off them and that there is a full and satisfactory conclusion to the whole process."
The Berwick-upon-Tweed MP told Channel 4: "The issue of the bus and that being national spending was very clearly made at the time.
"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."
Morecambe and Lunesdale MP David Morris is one of three MPs known 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 did not want a visit from the battle bus campaign at the centre of many of the claims about election spending breaches.
The Conservatives have insisted that the busloads of activists sent to key seats formed part of the national campaign spend rather than falling within the lower constituency limits.
Mr 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 battle bus project, saying it was a national spend."
He added: "I honestly believe not one MP is guilty of anything."
He said his case was straightforward: "We did not want the battle bus, and that was said from day one.
"We got the battle bus, we were instructed to have the battle bus, which is the same for everybody else, which is what the parties do."
The disclosure follows reports that Craig Mackinlay, who fought off a challenge from former Ukip leader Nigel Farage to hold Thanet South for the Tories, had been questioned for six hours last week by Kent Police.
Colchester's Will Quince also revealed that he had been interviewed by police and told he faced no further action.
Mr Quince voluntarily attended an interview under caution with Essex Police last January.
Essex is not one of the forces that has submitted files to the CPS.
But a CPS spokesman said it had received files from: Avon & Somerset, Cumbria, Derbyshire, Devon & Cornwall, Gloucestershire, Greater Manchester, Lincolnshire, the Metropolitan Police, Northamptonshire, Nottinghamshire and West Yorkshire police.
Once it has received a file, the CPS will decide whether to charge anyone.
The files were "all under consideration", a spokesman said.
A 12th force - Staffordshire - said it had also sent a file to the CPS.
In a statement posted on his Twitter feed, Mr Quince welcomed the decision by Essex Police but said the complaint against him had been "vexatious and politically motivated".
In his statement, Mr Quince acknowledged that once a formal complaint had been made in June 2016, police had a duty to carry out a thorough investigation.
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.
He said: "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."
Other MPs have directed their anger at Conservative Campaign Headquarters (CCHQ), complaining that they had been cut adrift by the party's high command even though the complaints relate to the busing of activists to campaign in key marginal seats, which was organised centrally.
In a leaked email to Sir Patrick, Lincoln MP Karl McCartney complained they felt "completely cast adrift" and had been "left to fend for themselves".
In a statement, Mr McCartney said he had made clear his "forthright views" privately to a number of senior party figures on behalf of backbenchers.