Sir Keir Starmer could be forced into a decision over Angela Rayner’s future, as the prime minister’s ethics adviser is expected to deliver his verdict on the Labour deputy’s tax affairs today.

Rayner, who is also the housing secretary, has been under mounting pressure since she admitted not paying the correct amount of stamp duty on an £800,000 flat in Hove, East Sussex.

She has argued the mistake was made as a result of incorrect advice from a conveyancer and two trust law experts, who told her she did not need to pay the higher rate reserved for second home purchases.

Her case was thrust into doubt late on Thursday when the conveyancing firm – Verrico & Associates – said it did not provide advice and had been made “scapegoats” in the political row.

Its managing director, Joanna Verrico, told The Telegraph while it had acted for Ms Rayner when she bought the property, no tax or trust advice was provided.

Any advice she may have received will form a key plank of an investigation by Starmer’s independent ethics guru, Sir Laurie Magnus, who Rayner referred herself to earlier this week.

Downing Street has said the prime minister expects a “quick” verdict, and he has refused to rule out sacking his second-in-command.

“I will act on whatever the report is that’s put in front of me,” Starmer told the BBC on Thursday – and that report may well arrive on his desk today.

Sir Laurie has concluded investigations into ex-ministers Nadhim Zahawi and Tulip Siddiq within days – and Sky News chief political correspondent Jon Craig reports he’s due to go on holiday on Saturday.

He is assessing whether Rayner broke ministerial rules, which place an “overarching duty on ministers to comply with the law”, “behave in a way that upholds the highest standards of propriety”, and “be as open as possible” with the public.

Conservative leader Kemi Badenoch has said Rayner must go.