Angela Rayner's family home was overvalued by more than £150,000 after what has been described as an "error" by lawyers.
The Ashton-under-Lyne property was increased from £487,500 to £650,000 in April last year, documents seen by the Telegraph indicated.
Ms Rayner sold her stake in the property to a trust, which was set up for her disabled son for £162,500, months later.
It was the same amount as the rise in property price.
The increase meant the property for the former Deputy Prime Minister and Housing Minister, who resigned from her positions in the Government last week, was almost twice as much as other homes on the street.
The documents surfaced days after her resignation after it was revealed she underpaid £40,000 in stamp duty.
Ms Rayner's critics say she has further questions to answer after the Asthon-under-Lyne revelation.
The rise in price occurred after lawyers from Shoosmiths conveyancing arm, Swiitch, the court-appointed law firm running the trust for Ms Rayner's son, wrote to the Land Registry in April last year.
Angela Rayner resigned as Deputy Prime Minister on Friday afternoon | HOUSE OF COMMONSThe firm apologised for an "original error", meaning the house had been registered at only 75 per cent of its value and formally applied for this higher value to be listed.
The trust was established following a compensation payout from the NHS in 2020.
It came after difficulties during her son's birth and the following care in 2008.
The rise in price saw Ms Rayner's share worth £162,500.
Angela Rayner during an interview where she admitted wrongdoing over her tax affairs last Wednesday
| GB NEWSThe former Deputy Prime Minister sold it to the trust and used the money to pay the deposit on her £800,000 flat in Hove.
Ms Rayner was being investigated at that time over whether she paid the correct tax on a former council house she used to own in Stockport.
However, she was later cleared of any wrongdoing.
Ms Rayner has also referred herself to the HMRC over her failure to pay the £70,000 stamp duty due on her Hove flat. She instead paid £30,000.
Ms Rayner resigned on Friday after the independent ethics adviser for the Government found she had broken the ministerial code due to ignoring two warnings that she should look for expert advice.
The lawyers involved in the purchase of the seaside flat had claimed they were being made "scapegoats" by the former Deputy Prime Minister and had not given her tax advice.
It was revealed that in the last year, no house within a mile of her home had sold for more than £561,000.
Sources have suggested that the true value of the home could be lower than £650,000 - however, it is understood to be bigger than others in the area.
A Swiitch spokesman told the Telegraph: "At the time of lodging papers with the Land Registry regarding the Ashton-under-Lyne property, an administrative error was made which bears no wider significance".
"The error was identified, and the matter was resolved satisfactorily with the Land Registry," the spokesman said.
It is understood the home was valued by a qualified independent surveyor.