This article is more than 6 months old

This article is more than 6 months old

Priti Patel has been accused of bullying a third senior civil servant when she was the secretary of state for international development.

Whitehall sources told the Guardian that the home secretary, who is already reeling from allegations that she bullied her permanent secretary at the Home Office and an aide in the Department for Work and Pensions, had “harassed and belittled” staff in her private office in 2017.

The allegations have been denied by sources close to Patel but will increase pressure on Boris Johnson to ask his minister to step aside while she is investigated by the Cabinet Office.

Sir Philip Rutnam, who resigned dramatically on Saturday as Home Office permanent secretary, is suing the government for constructive dismissal, claiming that Patel bullied and harassed staff in the Home Office.

It was claimed on Tuesday night that she also repeatedly harassed and belittled a staff member in her office at the Department for International Development (DfID).

According to BBC’s Newsnight, the Cabinet Office was aware of these claims and an alleged witness from DfID said they would be willing to give evidence at Rutnam’s employment tribunal.

A Tory source told the programme that members of the civil service were attacking Patel because they were trying to scupper government plans for immigration and the police. “Dark forces are trying to influence the findings of a cabinet office inquiry,” the source said.

Rutnam quit after accusing Patel of orchestrating a “vicious” campaign against him, of lying about her involvement in it and of creating a climate of fear in her department.

It emerged on Monday that another former aide to Patel received a £25,000 government payout after a threatened lawsuit in which the minister was named. According to the BBC, Patel was accused of shouting at the aide to “get lost” and “get out of her face”.

Patel shouted at the former aide with “unprovoked aggression” before removing her from her job, a BBC report claimed. Legal correspondence alleges that the civil servant took an overdose of prescription medicine shortly after the October 2015 incident.

A spokesperson for Patel said: “The home secretary completely rejects all allegations made against her.”

The latest claims against the home secretary came after the prime minister’s key aide Dominic Cummings was accused of fostering a culture of bullying in Whitehall as details resurfaced of a case in which he allegedly intimidated a mandarin who received a payoff.

The senior civil servant received about £25,000 in January 2013 after a lengthy grievance procedure involving Cummings, who was then Michael Gove’s special adviser at the Department for Education (DfE).

Labour has accused Cummings and Gove of being behind a culture of intimidation of civil servants and has called for the inquiry into Patel to be “genuinely independent”.

Angela Rayner, the shadow education secretary, said: “It is clear that Cummings and Gove had a concerning track record at the [DfE], yet now they have positions of responsibility over the whole system.

“In light of this week’s events, it’s more important than ever that we get full disclosure of the facts. No inquiry will be credible without complete transparency, not just on one case but the whole culture of this government,” she said.

Cummings was an adviser to Gove in the DfE in 2012 when accused along with a colleague of bullying the senior aide. A departmental investigation cleared both men, and said no disciplinary action was necessary, but the final judgment made clear that their conduct had on occasions fallen short and their behaviour “has been perceived as intimidating”.

The civil servant lodged a case with a tribunal, the Observer first disclosed, where the allegations would have been heard in public, but negotiations led to an agreed financial settlement.

In further indication of tensions in Downing Street, No 10 has confirmed that the special adviser who confronted Cummings over his “unkindness” at a recent meeting is leaving the government.

Lynn Davidson, an aide to the defence secretary, Ben Wallace, was asked to move post as part of a reshuffle of special advisers (Spads) in February, government insiders said – before she publicly upbraided Cummings over his treatment of aides.

On 14 February, at the weekly Spad meeting, Davidson reportedly criticised Cummings over his approach to government advisers.

The confrontation came after Sajid Javid dramatically resigned as chancellor, rather than accept that five of his aides would be sacked and their posts absorbed into a new handpicked “Spad unit” to serve the Treasury and No 10.