Business Secretary Kwasi Kwarteng has apologised to Parliament’s standards watchdog after he publicly speculated about her future during the sleaze row as it engulfed the Government.

He suggested in a letter to Kathryn Stone on Monday that he may have “fallen short” of the ministerial code and conceded he should have spoken “more carefully”.

Mr Kwarteng was widely criticised for suggesting the Parliamentary Commissioner for Standards should consider her position in the wake of the Owen Paterson row.

It was Ms Stone’s investigation that found the then-Tory MP breached the Commons code of conduct by lobbying ministers and officials for two companies paying him more than £100,000 per year.

As the Government came under intense criticism for its ultimately botched attempt to overhaul the standards system to protect Mr Paterson from suspension, Mr Kwarteng said it was “difficult to see what the future of the commissioner is”.

Mr Kwarteng has now apologised over his comments in a letter sent to Ms Stone and copied to Boris Johnson’s adviser on ministers’ interests, Lord Geidt.

“Having seen how my remarks have been interpreted, and reflecting on them, I recognise that in answering the question that was posed to me I should have chosen my words more carefully,” the minister wrote.

“I did not mean to express doubt about your ability to discharge your role and I apologise for any upset or distress my choice of words may have caused.

“I recognise that it is incumbent on ministers to adhere to the high standards of the ministerial code, including ensuring that our words are carefully chosen and that we treat others with consideration and respect.

“I therefore regret if the words I used on this occasion have given the impression of having fallen short of these high standards.”

Deputy Labour leader Angela Rayner has demanded that Lord Geidt carries out an investigation, suggesting Mr Kwarteng’s comments could amount to bullying an official.

Hours before the Prime Minister U-turned on the bid to prevent Mr Paterson’s suspension, Mr Kwarteng was asked on Sky News whether he thought Ms Stone should resign.

“I think it’s difficult to see what the future of the commissioner is, given the fact that we’re reviewing the process, and we’re overturning and trying to reform this whole process, but it’s up to the commissioner to decide her position,” he replied.

Pushed on what he meant by “decide her position”, Mr Kwarteng said: “It’s up to her to do that. I mean, it’s up to anyone where they’ve made a judgment and people have sought to change that, to consider their position, that’s a natural thing, but I’m not saying she should resign.”