David Cameron, from Number10, Downing street, was invited to the election TV debate just before Christmas.
An invoice for £150,000.95 was sent by his election rival’s offices, who said Cameron’s non-attendance left the parties out of pocket and his campaigners had their details to tell them he was not going.
Cameron’s election campaign officer said he had been told he would be taken to the small claims court for refusing to pay.
Election campaigners for the Conservative party found the invoice in a brown envelope in Cameron’s lunch bag last week.
Mr Taunton, a spin doctor for the Tories said: “It was a proper invoice with full official details and even had bank details on it.
“I can understand that they’re upset about losing campaign funds. The money isn’t the issue, it’s the way the way they went about trying to get the money from us.”