A Reform UK government would expect to dismiss the top civil servant in every government department and replace them with people seen as more likely to implement the party’s priorities, the Guardian has learned.

Senior Reform figures have concluded that the current crop of permanent secretaries, the lead civil servant in each department, are not up to the necessary standard. Some would be replaced by outsiders, and others by existing officials viewed as more suitable.

The plan has prompted warnings that a shift towards a less stable and more politicised civil service could result in the loss of significant expertise and of institutional memory, and would make government less effective.

Nigel Farage’s party has promised it will enact a radical programme. One senior member said this would be modelled on the second Trump administration, with a focus on making change via executive orders rather than legislation, where possible.

Reform has already said it would look at appointing outside experts to become ministers. It is understood that as well as making some into peers, so they could sit in the House of Lords, others considered for ministerial jobs would be lined up for winnable Commons seats.

While the party has received a series of big donations in recent months, including £12m from the crypto investor Christopher Harborne, it is expected that donors would be ruled out for ministerial roles.

The influx of money has allowed Reform to expand its teams working on new policies and preparation for government. This process thus far has had limited input from Farage, with insiders saying the party leader is focusing on May’s elections across England, Scotland and Wales.

A number of other countries have senior officials who are politicised and change with governments, notably the US. In the UK, existing rules allow ministers to fast-track outsiders into the civil service as “exceptional appointments” on two-year terms.

But unions and experts said Reform’s plans risked hampering the work of ministers rather than improving it.

“An ideological purge does not make for good government,” said Dave Penman, the general secretary of the FDA, the union for senior civil servants. “You would lose experience and institutional memory, but you would also send a message to the rest of the civil service that they are not trusted.

“Every civil servant knows they have to serve the government of the day. It’s absolutely clear – you serve or you go. There is no real evidence that the civil service would get in the way.

“How do you expect to bring in the brightest and the best if you then throw them under a bus? This would attract believers, but not necessarily the best people. And it shouldn’t be about what people believe. It’s about what they can do.

“Another problem is that as soon as you have political picks, when you change the minister they will want their own pick as well. In the last 10 years we have had whole football teams of secretaries of state. If you changed the permanent secretary every time, it would be a massive churn, and very disruptive.”

Alex Thomas, from the Institute for Government thinktank, said there was an obvious argument for civil servants to be set a clear direction.

He went on: “The question is what is effective. A blanket dismissal of the whole of the top of civil service would be removing an enormous amount of experience, expertise, and knowledge of how to make government do its job.

“If the intent is shock and awe, I would be surprised if it works. The history of government reform shows that people who succeed are those who galvanise, find allies and work with the system, rather than going to war with it.”

Reform UK was contacted for comment.