The Conservative candidate for South Thanet has been charged for alleged overspending in the 2015 general election campaign.
Craig Mackinlay, who is running again on 8 June, stands accused under the Representation of the People Act 1983, alongside his election agent Nathan Gray and party activist Marion Little.
The Conservative Party said the allegations were unfounded.
Other Tory candidates have been cleared of national battle bus campaigning.
Police forces have been investigating whether MPs’ agents should have filed costs for battle bus visits to constituencies under local expenses.
The Conservative Party said they had been campaigning “across the country for the return of a Conservative government” and, as a result, associated costs were regarded as national and not local expenditure.
Craig Mackinlay, 50, his agent Nathan Gray, 28, and Marion Little, a party activist, 62, have each been charged with offences under the Representation of the People Act 1983 and are due to appear at Westminster Magistrates’ Court on 4 July 2017.
Can Craig Mackinlay still stand?
Analysis by Helen Catt – BBC South East Today Political Editor
It may feel like a curve ball this close to polling day, but in electoral terms the decision to charge Craig Mackinlay means no change.
Postal ballots have already been sent out, the deadline for withdrawing nominations has passed, so there is no choice for the Conservatives to make, even if they wanted to: Craig Mackinlay will be the party’s candidate on the ballot paper in South Thanet.
If he were to win, he would also be able to take his seat like any other MP; being charged with a criminal offence does not preclude that.
The Conservative party could always decide to withdraw the whip, leaving him as an Independent, but that is unlikely in this case.
Nick Vamos, CPS 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.”
A Conservative Party spokesman said: “The legal authorities have previously cleared Conservative candidates who faced numerous politically motivated and unfounded complaints over the Party’s national Battlebus campaigning.
“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.”
Election laws were confused and unclear and the party was committed to strengthening future electoral laws, the statement added.
Reacting to news of the charge, the defeated 2015 UKIP candidate Nigel Farage, said earlier: “Oh my good lord, right that’s big news.”