A Conservative MP is being sued by the expenses watchdog after refusing to repay profits on his taxpayer-funded home.
Stewart Jackson has been asked to hand back £54,000 as potential capital gains made on the home since MPs were barred from claiming for mortgage interest.
But the MP for Peterborough has refused, the Independent Parliamentary Standards Authority (Ipsa) revealed.
An Ipsa spokesman said: "We have issued proceedings in the High Court".
The spokesman added: "He has been given every opportunity for it not to reach this stage."
But Jackson accused Ipsa of "trying to bully me into submission."
MPs were barred from claiming for mortgage interest on second homes in 2010, in the wake of public fury over "flipping" and other abuses.
Transitional arrangements were put in place to allow MPs time to sell their homes or make other plans - but they were not allowed to keep any capital gains arising during the two-year window.
On Thursday, Ipsa announced that 70 MPs would hand back almost £500,000 worth of profits. The cash was either paid in full or through a repayment plan where it would cause "exceptional hardship", Ipsa said.
Jackson, who has not sold the property, is the only member not to agree to a repayment.
The MP said: "IPSA’s legal proceedings are heavy handed and disproptionate and are clearly intended to bully me into submission."
The dispute relates to the valuations made of the home in 2010 and 2012, he said. Jackson said the property in question was his family home.
He claimed the value of the home had in fact fallen, whereas Ipsa said it had gone up by 20%, and said a "reasonable offer" had been made to the watchdog.
"Ipsa have negotiated with 70 other MPs in a secretive and arbitrary manner but in respect of my case, regrettably, they have refused to negotiate.
"I am merely seeking fair play and consistency and will pursue legal action to receive it.”
Welsh Secretary David Jones repaid the largest amount, £81,446.
Other MPs repaying money included Environment Secretary Owen Paterson (£7,755), Minsiter Without Portfolio Ken Clarke (£737), and Defence Secretary Philip Hammond (£34,883).