The former Northampton South MP has confirmed police have interviewed him under caution as part of the ongoing Sixfields 'missing millions' investigation.
The 39-year-old politician was leader of Northampton Borough Council when a £12 million loan to Northampton Town Football Club was made.
The funds were meant to pay for a new East Stand to be developed at Sixfields, but the structure was never completed.
The company that managed the project, 1st Land Limited, went into liquidation in early 2015, owing millions to contractors.
In September that year, it emerged the football club had also failed to make loan repayments to the borough council, and in November a fraud investigation was launched by police.
So far seven individuals have been arrested and bailed as part of the investigation, though a number of people have been interviewed under caution, including the former borough council chief executive David Kennedy.
But yesterday it emerged David Mackintosh has also been interviewed by police.
The BBC has quoted a member of the public who says she saw items in clear plastic bags being removed from the former MP's house in Great Billing.
Mr Mackintosh said: "I attended an interview on a voluntary basis to assist Northamptonshire Police with their general enquiries.
"As this is an ongoing matter I will not be commenting further at this stage but I very much welcomed the opportunity to speak with them."
And a spokesman for Northamptonshire Police added: "During the course of this week a 39-year-old man from Northampton has been assisting officers investigating the missing Sixfields development money.”
“The individual attended for voluntary interview under caution.”
Mr Mackintosh stood down as Northampton South MP in 2017 after members of the local party said they would vote to de-select him.
In an earlier statement released in September, police said more than 500 statements had been taken and more than 2,100 exhibits seized. Police said, at the time, that seven individuals had been arrested and a further nine interviewed at length under caution.