David Cameron has said he is confident the Tory party has done "nothing untoward" amid allegations of election expenses overspending.
The Prime Minister was speaking to Channel 4 News about claims that spending on transporting activists to campaign in key marginal seats in the 2015 general election was not properly recorded.
The Conservatives are facing an Electoral Commission probe and police inquiries over the allegations.
Mr Cameron said he was in favour of a full investigation and there were no questions his party would be unable to answer.
He said: "It's very important all these things are investigated, I'm very happy for us to answer all the questions about it, I don't think that there are any questions that anyone is asking that we can't answer and... I think it will put it beyond doubt."
The inquiries relate to whether the costs of sending activists to key constituencies around the country should have been recorded under individual candidates' limits, rather than as part of the national campaign.
Mr Cameron insisted that the expenses had been recorded correctly under the national cap.
He said: "I think it is a relatively straightforward set of questions that we have to answer.
"I'm very confident we're going to answer all of them and put this issue comfortably away. Because at the end of the day, as far as I can see, all parties have national bus tours, that's a national expense.
"All parties have associated expenses with those national bus tours, and I'm very confident that the party chairman and all the investigations will be able to answer all of these questions and... I'm taking it seriously because it's a serious issue but I'm confident that there's nothing untoward here."
He said he was taking the inquiries "very seriously" despite the Electoral Commission going to the High Court for an information disclosure order to seek the documents from his party.
Mr Cameron said the court order was not necessary as the watchdog had been given a delivery date for the paperwork.