Angela Rayner ©House of Commons

The admission follows days of denials and has left the Housing Secretary fighting for her political survival.

Ms Rayner now owes HM Revenue & Customs after paying £30,000 in stamp duty on an £800,000 flat in Hove, when the correct amount should have been £70,000 due to it being classed as a second home.

According to Labour figures, Ms Rayner consulted a conveyancer and two experts on trust law before the purchase in May. She believed she was not liable for the higher tax rate due to her complex living arrangements following a divorce. She had sold her stake in her constituency home in Greater Manchester to a trust established for her disabled son. However, new tax advice received this week confirmed she was still liable because of her son’s age and her role as a trustee, Financial Times reports.

Senior colleagues have rallied to her defence. Chancellor Rachel Reeves stated she has “full confidence” in Ms Rayner, acknowledging: “That was an error, that was a mistake. She is working hard now to rectify that, in contact with HMRC to make sure that the correct tax is paid.”

The matter is now the subject of an inquiry by Downing Street’s ethics adviser, Sir Laurie Magnus.