Ministers should behave professionally and courteously when dealing with civil servants and could be given training if they fail to do so, the UK’s most senior civil servant has told MPs. Giving evidence to the Commons public administration and constitutional affairs committee, Sir Mark Sedwill said he could not comment directly on allegations of bullying against the home secretary, Priti Patel, who has been accused of verbally abusing staff in three government departments. The cabinet secretary said, however, that there was an expectation ministers should conduct themselves properly and try to get the best out of their civil servants. He agreed that they could be sent for training if they had difficulties managing staff. “That is the most effective way of delivering the government’s agenda. If it doesn’t work then it doesn’t work and we will take whatever the appropriate action might be,” he said. The committee questioned Sedwill about the resignation last week of Sir Philip Rutnam as the Home Office’s permanent secretary. Rutnam plans to sue the government for constructive dismissal after a series of clashes with Patel. Part of his case is expected to include allegations that she bullied several civil servants in the department. She is also alleged to have mistreated staff in the Department for International Development and the Department for Work and Pensions. Senior Conservatives have argued for a new definition of bullying to be written into the ministerial code to avoid similar clashes in the future. Sedwill told MPs he did not think a more formal process was needed to allow permanent secretaries to air grievances about a minister’s conduct, and he described the fallout between Rutnam and Patel as regrettable. Asked whether the “informality of the process was wanting”, he replied: “I don’t think so because I think this is clearly a very regrettable incident. I regret Philip Rutnam’s decision to resign and hoped it could have been avoided. We have to allow that case and indeed the other investigation to take their course. “I don’t think we should necessarily try to write further regulations around relationships when the vast majority of cases are conducted professionally and in accordance with both the letter and the spirit of the various codes. There are tensions and differences, we deal with those when they arise. In general, I think the mechanisms we have available to us are adequate to the task. “Our expectation is that these are professional people, as in any big organisation. The job of the civil service is to support ministers, build a relationship of confidence and trust with them.” Sedwill declined to share the advice he had given the prime minister over the row. Asked whether it would still be regarded a private matter at an employment tribunal, he said: “I don’t know, I’d have to seek advice of legal counsel in those circumstances. But I would not expect at all for private advice between the cabinet secretary and the prime minister to be subject to that kind of procedure.” MPs asked Sedwill about remarks by Dominic Cummings, Boris Johnson’s key aide, that the government would benefit from having more “weirdos and misfits” in its ranks. He said: “Anything that widens the aperture of public service … I think is a good thing.” Asked about the government’s decision to hire Andrew Sabisky, who stood down as a No 10 adviser after it was disclosed that he had argued that intelligence was linked to race, Sedwill said Sabisky was a contractor, not a special adviser, and would have been subject to security vetting. “There is a distinction between someone with controversial views and someone who is a national security risk,” he said. Following controversy over the recruitment and dismissal of special advisers – Cummings is reported to have taken control of all politically appointed ministerial advisers, much to their anger – Sedwill said “only the prime minister” was able to hire and fire them.