Priti Patel has said she regrets the resignation of her former top civil servant Sir Philip Rutnam amid bullying allegations against her.
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”.
She said she “deeply cared” about the “wellbeing” of her civil servants and valued their professionalism.
Sir Philip said he had been forced out of his job after a “vicious” campaign.
The prime minister has given Mrs Patel her support but the Cabinet Office is investigating whether she broke the ministerial code.
Ms Patel has not commented publicly on the allegations her, but government sources have said she denies them.
Resigning from his position on Saturday, Sir Philip said he had received allegations that Ms Patel’s conduct towards employees included “swearing, belittling people, making unreasonable and repeated demands”.
He said she had failed to disassociate herself from press briefings against him and he now intended to take legal action against the Home Office on the basis of constructive dismissal.
In the internal email to home office staff, Mrs Patel thanked Sir Philip for his “long and dedicated career of public service” and praised the civil service for the support they gave to ministers.
The e-mail, co-written Sir Philip’s acting successor Shona Dunn, adds: “We both regret Sir Philip’s decision to resign.
“We both deeply value the work that every person in this department does and care about the wellbeing of all our staff.
“It is therefore a time for us all to come together as one team.
“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.”
She also insisted that she would continue to “drive forward” her priorities, including tackling violent crime and drugs gangs as well as implementing the biggest changes to the UK’s immigration system in a generation after Brexit.
“We will drive these priorities and move forward, across our operational community, both in the department and beyond, working tirelessly to ensure that we keep this country safe and prosperous.”
The Cabinet Office is leading an internal inquiry to “establish the facts” regarding Sir Philip’s claims and whether they represented a breach of the ministerial code.
Labour has called for Mrs Patel to resign while the First Division Association union, which represents civil servants, has called for an “independent” inquiry into Ms Patel’s behaviour to be led by an external lawyer.
It emerged on Monday that a former aide to Mrs Patel received a £25,000 payout from the government after claiming she was bullied by the then employment minister.
Legal correspondence seen by the BBC alleges the woman took an overdose of prescription medicine following the alleged incident in 2015. The DWP did not admit liability and the case did not come before a tribunal.