Home Secretary Priti Patel is facing allegations of bullying staff in a third government department.
A senior official at the Department for International Development (DfID) reported a "tsunami" of allegations of abuse by officials in her private office when she was secretary of state, BBC2's Newsnight reported.
The claims follow the resignation at the weekend of the top official at the Home Office, Sir Philip Rutnam, who quit accusing her of bullying subordinates.
A former aide at the Department for Works and Pensions is also reported to have received a £25,000 payout from the Government after claiming she was bullied by Ms Patel when she was employment minister.
A spokesman for Ms Patel said: "The Home Secretary categorically denies all of these allegations."
Newsnight quoted a Tory source as saying there was a "concerted effort" by sections of the Civil Service to undermine Ms Patel and that "dark forces" were trying to influence a Cabinet Office inquiry into her conduct.
Johnson silent over when he first knew of Priti Patel bullying allegations
Vanessa Feltz (left) sips tea with newly elected Witham MP Priti Patel during an event supporting Breast Cancer Care's Strawberry Tea fundraising campaign at the Houses of Parliament, Westminster, London.
Prime Minister David Cameron speaks with Witham MP Priti Patel in front of the Shah Sayyid Tomb in the Lodi Gardens in Delhi, India.
Prime Minister David Cameron and Witham MP Priti Patel, walk through Kolkata, India, where they visited the Howrah Bridge which was built by the Cleveland Bridge and Engineering Company.
Priti Patel who is the new Employment Minister, arrives at 10 Downing Street in London, as the PM puts the finishing touches to his new cabinet.
(left to right) Justice Secretary Michael Gove, Minister for Employment Priti Patel and Works and Pensions Secretary Iain Duncan Smith arrive in Downing Street to take part in the first Cabinet meeting since the Conservative Party won the General Election.
Indian Prime Minister Narendra Modi (centre) is flanked by Minister of State for the Foreign and Commonwealth Office, Hugo Swire (left) and Priti Patel (right) as he arrives at Heathrow Airport, London, for an official three day visit.
Employment minister Priti Patel launches a new government scheme to give extra careers advice to school pupils during a visit to Holy Trinity Catholic School in Birmingham.
(Left to right) John Whittingdale, Theresa Villiers, Michael Gove, Chris Grayling, Iain Duncan Smith and Priti Patel attend the launch of the Vote Leave campaign at the group's headquarters in central London.
EDITORIAL USE ONLY Minister for Employment Priti Patel tries her hand at painting with Matt Gray, Painting Skills Development Manager and Matt Pullen, CEO of AkzoNobel, as she officially opens AkzoNobel's Dulux Academy, the UK's first training facility dedicated to painters and decorators, Slough, Surrey.
Works and Pensions Secretary Stephen Crabb and Minister for Employment Priti Patel arrive for a Cabinet meeting in Downing Street, London.
Boris Johnson and Priti Patel meet workers at clothing and uniform manufacturers Simon Jersey in Accrington, Lancashire, during a visit as part of the Vote Leave EU referendum campaign.
Priti Patel speaks at a rally with Boris Johnson and Michael Gove (right) in Preston town centre, Lancashire, as part of the Vote Leave EU referendum campaign.
Michael Gove, Boris Johnson (centre) and Priti Patel pull pints of beer at the Old Chapel pub in Darwen in Lancashire, as part of the Vote Leave EU referendum campaign.
(left to right) Boris Johnson, Priti Patel and Michael Gove during a visit to Farmhouse Biscuits in Nelson, Lancashire, where they were campaigning on behalf of the Vote Leave EU referendum campaign.
Boris Johnson auctions a cow during a visit to a cattle auction in Clitheroe in Lancashire, where he along with Priti Patel and Michael Gove are campaigning on behalf of the Vote Leave EU referendum campaign.
Priti Patel MP visits Shree Sanatan Hindu Mandir Temple in Wembley, London, whilst out campaigning on behalf of the Vote Leave campaign.
Priti Patel arrives at White Waltham Airfield in Maidenhead, Berkshire, to meet veterans who will outline why they are voting to leave the EU.
(Left-right) Foreign Secretary Boris Johnson, International Development Secretary Priti Patel, Prime Minister Theresa May, Home Secretary Amber Rudd and Health Secretary Jeremy Hunt during Prime Minister's Questions in the House of Commons, London.
The Prince of Wales and the Duchess of Cornwall with International Development Secretary Priti Patel (right) during a reception and dinner for supporters of the British Asian Trust at Guildhall, London.
Priti Patel (left) with Boris Johnson's father Stanley Johnson and sister Rachel Johnson watch him speaking at a fringe event at the Conservative Party annual conference at the International Convention Centre, Birmingham. (Photo by Stefan Rousseau/PA Images via Getty Images)
Prime Minister Boris Johnson and Home Secretary Priti Patel on a walkabout with local police during a visit to North Road, Harbourne, Birmingham before announcing his plan to recruit an extra 20,000 police officers and an urgent review will take place of plans to make it easier for forces to use stop-and-search powers.
Discover More Like This
BACK TO SLIDE
The latest claims relate to the period around 2017 when Ms Patel was sacked by Theresa May as international development secretary over unauthorised contacts with the Israeli government.
Following her dismissal, a senior figure in DfID was said to have approached staff in her private offices about allegations that they had heard of bullying.
The senior figure was said to have been told of multiple claims of staff being humiliated and coming under heavy pressure in emails – similar to the allegations made about Ms Patel's conduct at the Home Office.
The senior figure then went to see another senior figure in DfID and urged them to contact the then cabinet secretary – the late Sir Jeremy Heyward – so that her conduct recorded was "in the system" if she ever returned to government.
Although the person making the claims has not been named, they were said to be prepared to give evidence to the Cabinet Office inquiry currently under way into allegations she broke the ministerial code.
The individual concerned was also said to be ready to give evidence in support of Sir Philip – who is claiming constructive dismissal – if his case goes to an industrial tribunal.
A Tory source, quoted by Newsnight, hit back, saying: "What we are seeing is a concerted effort by certain sections of the Civil Service to undermine a Home Secretary trying to deliver what people want on crime and immigration.
"It is deeply disturbing that dark forces are trying to influence the findings of a Cabinet Office inquiry.
On Tuesday, Ms Patel expressed her "regret" at the decision of Sir Philip to quit and urged staff in the Home Office to come together as "one team".
In a joint email to staff written with Sir Philip's interim successor Shona Dunn, she insisted they cared about the wellbeing of all employees.
They expressed their gratitude to the staff for their continuing hard work and "commitment to deliver the Government's priorities".
"We both deeply value the work that every person in this department does and care about the well-being of all our staff. It is therefore a time for us all to come together as one team," they wrote.
"We also recognise the importance of candour, confidentiality and courtesy in building trust and confidence between ministers and civil servants.
"Both of us are fully committed to making sure the professionalism you would expect to support this is upheld."
Boris Johnson has expressed his full confidence in Ms Patel, who he promoted to one of the great offices of state after she had previously been sacked from the Cabinet by Theresa May.
However, some Tory MPs have questioned how much longer she can carry on in the job, while Labour has complained the inquiry into her conduct – to be carried out by the Cabinet Office – is not fully independent.