Craig MacKinlay, who beat then-UKIP leader Nigel Farage and comedian Al Murray in that campaign, is standing again on 8 June but is accused under the Representation of the People Act 1983, alongside his election agent Nathan Gray and party activist Marion Little. They are due to appear at Westminster Magistrates Court on 4 July 2017.

Several other Conservative candidates have been cleared of any wrongdoing.

The issue centres on whether costs for battle bus visits to constituencies should have been filed under local expenses.

As postal ballots have already been sent out and the deadline for withdrawing candidates has passed, MacKinlay will still be the Conservatives’ candidate in South Thanet on election day.

MacKinlay told CCH Daily the decision by the CPS to charge him was ‘shocking’.

‘I've done nothing wrong and I am confident that this will be made very clear as the matter progresses.

He added: ‘I am very disappointed with the way this has been handled by the CPS and Kent Police, and I must question the timing of this decision given that Kent Police confirmed on 18 April that their file had been sent to the CPS to review and make their decision: why leave this until a few days before the election?’

The Conservative party branded the allegations ‘unfounded’ and ‘politically motivated’.

The party said in a statement: ‘We continue to believe that this remaining allegation is unfounded. Our candidate has made clear that there was no intention by him or his campaigners to engage in any inappropriate activity. We believe that they have done nothing wrong, and we are confident that this will be proven as the matter progresses.

‘The individuals remain innocent unless otherwise proven guilty in a court of law.’

The statement added the rules around spending were confusing and the party would ‘strengthen’ them in the future.

Nick Vamos, Crown Prosecution Service head of special crime, said: ‘On 18 April we received a file of evidence from Kent Police concerning allegations relating to Conservative Party expenditure during the 2015 General Election campaign. We then asked for additional enquiries to be made in advance of the 11 June statutory time limit by when any charges needed to be authorised.

‘Those enquiries have now been completed and we have considered the evidence in accordance with the Code for Crown Prosecutors.

‘We have concluded there is sufficient evidence and it is in the public interest to authorise charges against three people. Criminal proceedings have now commenced and it is extremely important that there should be no reporting, commentary or sharing of information online which could in any way prejudice these proceedings.’

The ICAEW said in a statement: ‘Our disciplinary byelaws preclude us from commenting on whether any matter may or may not be the subject of consideration by our Professional Conduct Department. Where such consideration results in disciplinary action being taken then a public announcement will be made.

‘Although we cannot comment on any individual matters, those same byelaws state that a member shall be liable to disciplinary action if he commits any act or default likely to bring discredit on himself, the institute or the profession of accountancy.’