Another police fraud probe has been launched into whether the Tories breached spending rules securing their knife-edge general election win last year.
Lincolnshire Police said it was investigating as the Conservative Party handed over evidence regarding the controversy to the Electoral Commission.
The watchdog went to the High Court for an information disclosure order to seek the documents.
Senior Tories insisted that the legal action was not needed as they always intended to hand them over.
"We advised the Electoral Commission on 29th April that we would comply with their notices by 1pm today - and have done so. There was no need for them to make this application to the High Court," a spokeswoman said.
Allegations regarding breaches of spending rules centre on claims the Tories listed the costs of bussing activists into key marginal seats under national, rather than local, spending accounts.
Lincolnshire joins a number of police forces across the country, including Greater Manchester, Cheshire, and Devon and Cornwall, in probing Conservative activity.
A statement from Lincolnshire Police said: "We are aware of recent media reporting regarding allegations of irregularities in the election expenses of the Conservative Party and some of their candidates in the General Election 2015 and three by-elections in 2014. We can confirm that we are carrying out general enquiries, but we will not be commenting further until they are complete."
The Electoral Commission said it was forced to take the legal action because the Tories failed properly to act on two statutory notices requiring it to produce information - providing " limited disclosure of material in response to the first notice (issued on 18 February 2016) and no material in response to the second notice (issued on 23 March 2016)" - d espite being granted extensions to the original deadlines to comply.
Bob Posner, director of party and election finance and legal counsel, said: " If parties under investigation do not comply with our requirements for the disclosure of relevant material in reasonable time and after sufficient opportunity to do so, the Commission can seek recourse through the courts.
"We are today asking the court to require the party to fully disclose the documents and information we regard as necessary to effectively progress our investigation into the party's campaign spending returns."
The party acknowledges that some accommodation for the activists was not properly registered, but insists that the bus tour was part of the national campaign organised by Conservative campaign headquarters (CCHQ) and as such did not fall to be recorded in individual constituency spending limits.
The case has led to calls for the new Police and Crime Commissioner (PCC) for Devon and Cornwall to stand aside while she is investigated over her part in the campaign.
Alison Hernandez, who was elected PCC last week, was the agent for Conservative candidate Kevin Foster in Torbay, one of the constituencies involved.
The Commission said it had received additional information from the party and had begun assessing whether it fulfilled the requirements of the orders.