Britain’s Deputy Prime Minister Angela Rayner resigned on Friday after an investigation concluded she breached the ministerial code by underpaying property tax, dealing a major setback to Prime Minister Keir Starmer’s Labour government.

Rayner, a prominent figure within Labour’s left wing, admitted earlier this week to underpaying a surcharge on a flat purchase and referred herself to the government’s independent ethics adviser.

In a letter to Starmer, ethics chief Laurie Magnus stated that Rayner ignored legal advice she had received, which constituted a breach of the code.

In her resignation letter, Rayner wrote, “I accept that I did not meet the highest standards,” confirming she was stepping down as both deputy prime minister and housing minister. She added, “I deeply regret my decision to not seek additional specialist tax advice. I take full responsibility for this error.”

Responding, Starmer said he was “very sad” to lose her from government, but assured her she would “remain a major figure in our party.”

Rayner’s exit compounds the difficulties facing Starmer’s administration, which has already faced backlash over U-turns on welfare reforms and fuel benefits for pensioners. Its inability to curb illegal small boat crossings has also boosted Nigel Farage’s Reform UK party, which now leads Labour in national polls.

Rayner revealed on Wednesday that she had underpaid stamp duty on a seaside flat in southern England after reports alleged she had saved £40,000 ($53,000) by removing her name from the deeds of another property.