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Home Secretary Priti Patel has been accused of bullying staff at a third government department, BBC Newsnight has learned.

The claims are from her time as International Development Secretary from 2016 to 2017, and follow similar claims at the Home Office and the Department for Work and Pensions.

A Tory source said "dark forces" were trying to influence an inquiry into Ms Patel's conduct in her current role.

Ms Patel denies all the allegations.

The latest claims were reportedly brought to a senior official at the Department for International Development after she quit as its Secretary of State in 2017.

The BBC reported on Monday that an official in the Department for Work and Pensions (DWP) received a £25,000 payout after alleging she was bullied by Ms Patel in 2015 during her time as employment minister.

The DWP did not admit liability and the case did not come before a tribunal.

Newsnight has now learned that in 2017, Ms Patel was allegedly accused by officials in her private office at DfID of humiliating civil servants in front of others, of putting heavy pressure in emails and of creating a general sense that "everyone is hopeless".

The allegations were described to the programme as similar to those levelled against Ms Patel by Sir Philip Rutnam, who resigned as Home Office permanent secretary on Saturday.

The latest claims to come to light were reportedly passed in 2017 to the DfID official by another senior figure in the department - who advised that the cabinet secretary at the time, the late Lord Heywood, should be informed.

The senior figure wanted the allegations to be lodged in the Whitehall system so that officials would be aware of allegations surrounding Ms Patel if, as expected, she returned to ministerial office.

Ms Patel resigned as Secretary of State for International Development in November 2017 over an unauthorised visit to Israel.

A Home Office spokesperson said: "The home secretary categorically rejects all of these allegations."

A source from the Conservative Party told Newsnight: "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."

Michael Gove, the Chancellor of the Duchy of Lancaster, announced on Monday that a Cabinet Office inquiry would seek to "establish the facts" around Ms Patel's conduct as home secretary.

She has faced allegations of having broken the ministerial code in the wake of allegations aired by Sir Philip when he resigned.

Sir Philip is suing the Home Office for constructive, unfair dismissal after Ms Patel allegedly refused to engage with him after a row over allegations of bullying against the home secretary.

In his resignation statement, Sir Philip said he did not believe her denials of involvement in "a vicious and orchestrated briefing campaign" against him.

Media playback is unsupported on your device Media caption Sir Philip Rutnam says there has been a "vicious, orchestrated briefing campaign" against him

Downing Street is standing by Ms Patel. But a cabinet minister told Newsnight that she would face political "armageddon" if Sir Philip's case for constructive dismissal makes it to a tribunal.

The minister expected that many other cases would come to light under legally binding disclosure rules in a tribunal.

The source who raised the allegations against Ms Patel at DfID in 2017 told Newsnight they were prepared to give evidence under their name to two official hearings.

These are the Cabinet Office inquiry into Ms Patel's conduct as home secretary and a tribunal if Sir Philip's case for constructive dismissal is granted a hearing.

On Tuesday, Ms Patel said she regretted Sir Philip's resignation.

In an e-mail to Home Office staff, she thanked him for his service but said it was "now time for the Home Office to come together as one team".