A spokesman for Mr McNulty insisted that the claims on the property in Harrow were entirely within the parliamentary rules on MPs' allowances.
Mr McNulty lived in the house in his Harrow East constituency with his parents before his 2002 marriage to second wife Christine.
After moving into her home in Hammersmith, west London, he claimed the second home allowance on the Harrow property, receiving around £60,000 since 2001-2, while his parents continued to live there.
In January this year, he decided to stop claiming the allowance as interest rates had fallen so far that he found he was able to meet his mortgage commitments from his MP's salary, said his spokesman.
The Additional Costs Allowance, worth up to £24,000 a year, is paid to MPs from outside inner London to cover the cost of staying away from their main home for the purpose of performing parliamentary duties.
Mr McNulty's spokesman insisted: "There is absolutely nothing irregular in Tony's situation."