Nadhim Zahawi has agreed to pay back money claimed on electricity which he used to heat his stables and a mobile home, as well as his constituency home.
The Stratford on Avon MP said he would repay the cash and had notified the parliamentary watchdog.
"Since last week’s coverage of my energy bills I have been looking into them further and can confirm that all claims for heating fuel relate purely to my second home. However I have made a mistake with my electricity claims," he wrote on his blog.
"On investigation I have discovered that the electricity supply for a mobile home located in the stable yard and for the stables themselves was linked to my house.
"Whilst a meter was installed in the stable yard I have only been receiving one bill, it was wrong to assume I was receiving two and to have not checked this sooner.
"I am mortified by this mistake and apologise unreservedly for it. I will obviously be paying back any money that was wrongly claimed immediately and have already contacted IPSA [the Independent Parliamentary Standards Authority] regarding the correct procedure to follow."
Report emerged last week that the Tory MP, who has been tipped for big things since he entered parliament in 2010, claimed about £6,000 in expenses for heating and electricity at his constituency property and second home in the year to March. Zahawi puts the figure at closer to £4,000.