Dominic Raab has been interviewed by the senior lawyer investigating allegations of bullying in an indication that the official inquiry could be drawing to a conclusion.

Multiple sources with knowledge of the investigation told the PA news agency that the Deputy Prime Minister had been questioned by senior lawyer Adam Tolley KC.

Dozens of witnesses including top departmental civil servants are believed to have spoken to the inquiry, which could determine Mr Raab’s political fate.

It was unclear how many times he had been interviewed or when. At the weekend, Mr Raab declined to say whether he had been questioned by Mr Tolley.

But Mr Raab, who is also Justice Secretary, told Sky’s Sophy Ridge On Sunday: “I will answer, as I said I would, all questions he’s got.”

Mr Raab denied bullying and insisted he had “behaved professionally throughout” but said he would resign if an allegation of bullying was upheld.

During the investigation, Mr Tolley would be expected to put the allegations to Mr Raab before finalising his report.

The Prime Minister has been resisting calls to suspend his deputy while under investigation, including from former Tory party chairman Sir Jake Berry, Labour and the FDA union which represents senior civil servants.

If the investigation is damning, Mr Sunak will again face questions about what he knew about the allegations before bringing Mr Raab back into the Cabinet.

Downing Street has only ruled out the Prime Minister being aware of “formal complaints”, but sources say he had been warned about his ally’s behaviour.

The eight formal complaints centre on Mr Raab’s tenures as foreign secretary, Brexit secretary and during his first stint as justice secretary.

Mr Raab ordered the investigation in November after coming under pressure following numerous claims, including that he was so demeaning to junior colleagues that many were “scared” to enter his office.