Opposition parties have called for an investigation into the behaviour of cabinet minister Dominic Raab over claims he mistreated staff during a previous stint as justice secretary.
The Guardian reported civil servants were offered a "route out" of working with him after his return in October.
The paper was told Mr Raab acted in a "rude" and "aggressive" manner between September 2021 and September 2022.
His spokesman said he "always acts with the utmost professionalism".
Mr Raab was sacked as justice secretary and deputy prime minister by former PM Liz Truss, but was reappointed to those roles by Rishi Sunak following his election as leader by Tory MPs.
The Guardian said it had spoken to multiple sources who claimed Mr Raab had created a "culture of fear" at the Ministry of Justice (MoJ), and who alleged his behaviour with civil servants had been "demeaning" and "very rude and aggressive".
The paper claimed several sources told it that about 15 members of staff from Mr Raab's private office were taken into a room where MoJ officials acknowledged they may be anxious about his return and gave them the option of moving roles.
It added it had been told that Antonia Romeo, the most senior civil servant in the MoJ, had spoken to Mr Raab on his return to the department to warn him that he must treat staff professionally and with respect.
Concerns have also been expressed to BBC News about Mr Raab's behaviour in meetings.
However, no formal complaints have been made against the cabinet minister.
Labour has described the allegations as "deeply troubling" and has called for them to be investigated "urgently and independently".
The party's deputy leader Angela Rayner said Prime Minister Rishi Sunak must "come clean" about whether he knew about the claims when he reappointed Mr Raab to the MoJ, and said it raised questions about the PM's judgement.
Ms Rayner said: "He claimed zero tolerance for bullying, promised a government of integrity and pledged to urgently appoint an ethics adviser, yet is falling far short on every promise.
"Rishi Sunak is already showing he is not just failing to stop the rot but letting it fester."
Liberal Democrat deputy leader Daisy Cooper said the Tory government did not have "a shred of integrity left".
"These latest reports are deeply disturbing and must be investigated immediately by the Cabinet Office," she said.
'Zero tolerance of bullying'
A source close to the justice secretary did not deny the option of a transfer was given to staff on his return, but pushed back against any suggestion of bullying.
And a spokesman for Mr Raab said: "Dominic has high standards, works hard, and expects a lot from his team as well as himself.
"He has worked well with officials to drive the government's agenda across Whitehall in multiple government departments and always acts with the utmost professionalism."
Meanwhile, some Conservative MPs have come to Mr Raab's defence.
Helen Grant, MP for Maidstone and the Weald, said she had witnessed a "very decent" minister with "high professional standards" when she worked with him when he was foreign secretary.
Michael Fabricant, MP for Lichfield, told the BBC the justice secretary was "demanding in a good way" and "business-like", but added "to say he is a bully I just don't see that".
A MoJ spokeswoman said: "There is zero tolerance for bullying across the civil service.
"The deputy prime minister leads a professional department, driving forward major reforms, where civil servants are valued and the level of ambition is high."
It comes after cabinet minister Sir Gavin Williamson resigned this week over allegations of bullying.
He is accused of sending abusive messages to a fellow Tory MP last month and of bullying a senior civil servant as defence secretary.
Sir Gavin said he "refuted" how his conduct had been characterised.