Whistleblowers from the Conservative Party have undermined official denials of breaking electoral law in the run-up to the 2015 general election.
The allegations centre around the Tory 'Battlebus2015' campaign, where campaigners were sent in buses to 29 marginal Conservative seats around the UK.
A Channel 4 investigation found the expenses from these buses were not noted in local spending reports.
It would have been a legal necessity to declare the expenses from the bus campaign if the campaigners were supporting the local Tory candidates in the area.
Tory officials dismissed this by insisting the activists were only disseminating the party's national message, meaning the expense would be national, and not in the local domain.
However Gregg and Louise Kinsell, who took part in the battlebus campaign, claimed this was untrue to Channel 4 and the party was "telling lies" about what they really did.
They claimed they weren't just there to pass on the national message, but also to support the local Conservative candidates in the areas they went to.
A number of police forces are investigating the claims, looking into the seats of more than 20 current Tory MPs.
A Conservative spokesman has said the party is co-operating with the police over the matter.