UPDATED: Conservative Stroud and Thornbury & Yate MP candidates will not be prosecuted over undeclared ‘battle bus’ expenses

Neil Carmichael and Luke Hall were both being investigated by the CPS in a process which enveloped 14 police forces, including Gloucestershire and Avon and Somerset Constabularies.

The investigation focused on whether the costs to transport and accommodate bus-loads of Conservative activists to marginal constituencies – more than £2,000 a day – should have been declared by candidates.

With parties having to submit their General Election prospects by tomorrow this decision could have left the Conservative Party scrambling to find new candidates.

Neil Carmichael said: "I welcome this decision by the Crown Prosecution Service which confirms I acted honestly and properly throughout the election campaign in 2015.

"I intend to now get on with talking to constituents about the policy issues that really matter to them in 2017 - education and the economy."

Luke Hall’s campaign expenditure would have exceeded the £14,709 limit by £568 if it included the battle-bus costs.

Conservative Party chairman Patrick McLoughlin said: “After a very thorough investigation, we are pleased that the legal authorities have confirmed what we believed was the case all along: that these Conservative candidates did nothing wrong.

"These were politically motivated and unfounded complaints that have wasted police time. We are glad that this matter is finally resolved.

“A number of false and malicious claims continue to be spread on the internet.

"People should be aware that making false claims about a candidate’s personal character and conduct is an electoral offence, as well as being defamatory.

“Notwithstanding these false claims, Conservatives want to strengthen election rules to safeguard electoral integrity – in light of the real and proven cases of electoral fraud exposed in Tower Hamlets in 2015.”

Nick Vamos, CPS head of special crime, said: "We have considered files of evidence from 14 police forces in respect of allegations relating to Conservative Party candidates' expenditure during the 2015 General Election campaign.

"We considered whether candidates and election agents working in constituencies that were visited by the Party's 'Battle Bus' may have committed a criminal offence by not declaring related expenditure on their local returns.

"Instead, as the Electoral Commission found in its report, these costs were recorded as national expenditure by the Party.

"We reviewed the files in accordance with the Code for Crown Prosecutors and have concluded the tests in the Code are not met and no criminal charges have been authorised.

"Under the Representation of the People Act, every candidate and agent must sign a declaration on the expenses return that to the best of their knowledge and belief it is a complete and correct return as required by law.

"It is an offence to knowingly make a false declaration.

"In order to bring a charge, it must be proved that a suspect knew the return was inaccurate and acted dishonestly in signing the declaration.

"Although there is evidence to suggest the returns may have been inaccurate, there is insufficient evidence to prove to the criminal standard that any candidate or agent was dishonest.

"The act also makes it a technical offence for an election agent to fail to deliver a true return.

"By omitting any 'Battle Bus' costs, the returns may have been inaccurate.

"However, it is clear agents were told by Conservative Party headquarters that the costs were part of the national campaign and it would not be possible to prove any agent acted knowingly or dishonestly.

"Therefore we have concluded it is not in the public interest to charge anyone referred to us with this offence."

"Our evaluation of the evidence is consistent with that of the Electoral Commission.

"While the role of the Commission is to regulate political finances and campaign spending, the role of the CPS is to consider whether any individual should face criminal charges, which is a different matter with different consideration and tests.

"One file, from Kent Police, was only recently received by the CPS, and remains under consideration.

"No inference as to whether any criminal charge may or may not be authorised in relation to this file should be drawn from this fact and we will announce our decision as soon as possible once we have considered the evidence in this matter."