Conservative MP Stewart Jackson was one of 29 MPs told to hand over a total of almost £500,000 to the Independent Parliamentary Standards Authority (Ipsa) to cover a proportion of the increased value of properties funded by their expenses.
Mr Jackson has said he is mounting his own legal challenge against Ipsa, which he accused of over-estimating the capital gain on his family home in his Peterborough constituency and then rushing into "heavy-handed and disproportionate" litigation to recover the sum. The other MPs involved have agreed to pay the sums demanded in full.
The watchdog moved to ban the use of Commons expenses to pay mortgage interest in May 2010, in the wake of public fury over "flipping" and other abuses. However, transitional arrangements were put in place permitting MPs elected before 2010 to keep claiming the money up to last August - as long as they agreed to return any potential capital gain.
In both of these cases - and that of Mr Jackson - the MPs were asked to repay more than they had received because the value of their property was calculated to have risen by more than the cost of the interest payments. Mr Jackson has refused to agree a repayment plan as he rejects the valuation placed on his property.
In a statement, the Peterborough MP said: "Ipsa's legal proceedings are heavy-handed and disproportionate, and are clearly intended to bully me into submission.
"The money which Ipsa is demanding retrospectively is more than the total amount I received when I was claiming mortgage interest and the property is now valued at less than we purchased it for in 2005. 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."
An Ipsa spokesman said: "One of the most damaging aspects of the expenses scandal was the practice where MPs got taxpayer support to own a second home. That is why we said we would stop this, and we have now done so.
"In valuing the property, it was important that we didn't rely on amateur valuations or guesses from the web. Instead, we demanded formal valuations at the start and end, from the Royal Institute of Chartered Surveyors - the most authoritative voice in this field. Stewart Jackson provided us with two RICS valuations. As he has been unwilling to pay the £54,000 due we have issued proceedings to recover the sum through the High Court."