Any move to amend the Civil Service code to remind officials to follow ministerial decisions on the Rwanda plan would be “desperate”, ministers have been warned.

Confirmation by illegal migration minister Michael Tomlinson that the Government was considering tweaking the Civil Service code to tackle the concerns of right-wing Tory MPs sparked a rapid and furious backlash from trade unions.

The minister told BBC Radio 4’s Today programme that the code could be tweaked in the face of concerns by backbench MPs that the proposed Rwanda legislation does not do enough block last-minute Rule 39 injunctions from the European Court of Human Rights.

“My expectation is that there will be further confirmation that it will be for ministers to decide and then, once those decisions are made, they will be carried out … by our excellent and efficient civil servants,” he said.

According to the Times, a less drastic option of sending a letter to officials reminding them of their duty to follow the decisions of ministers is also being considered.

The proposal to change the code was sharply criticised.

Dave Penman, general secretary of the FDA union which represents senior civil servants, said this would amount to ministers obliging officials to breach the law and would put civil servants in an “invidious position”.

“Ultimately the problem here is that what the Conservative Party are trying to do is resolve an unresolvable tension within their party about our obligations under the European Convention of Human Rights,” he told PA news agency.

He said ministers were “trying to put that onto civil servants who are going to have to make judgments around what an interpretation of the rule of law is, because they have an obligation to uphold the rule of law”.

“The ministerial code says you should not put civil servants in a position where there’s a conflict between their obligations under the civil service code and instructions you give them as a minister.

“Pretending that you can do that is not actually doing it because a civil servant has to deal with facts, not illusion or bluster or rhetoric”, he said.

Garry Graham, deputy general secretary of Prospect union, said: “The Civil Service code requires that civil servants provide objective advice to ministers based on a rigorous analysis of the evidence.

“They have a duty under the code to comply with the law and uphold the administration of justice.

“It is not for ministers to dictate the terms of the advice they receive.

“This is a desperate attempt by the party of government to placate their own backbenchers. It is vitally important for our democracy that Civil Service impartiality is not compromised.”

Some right-wing MPs have long hit out at Whitehall and civil servants, accusing them of helping to block the progress of the Rwanda plan and other measures to tackle illegal migration.

Former home secretary Dame Priti Patel urged the Prime Minister on Tuesday to ensure “all potential roadblocks are removed, including the Civil Service blob”.

The senior Tory said Mr Sunak should make clear that the “Civil Service code cannot be used by officials to obstruct decisions”.

But human rights lawyer Adam Wagner said any such plans would be “obviously a non-starter”.

“Civil servants can only advise on the basis of the law, and the government’s advice from the Attorney General and (barrister) Sir James Eadie apparently is, rightly, that Rule 39 measures must be complied with in order not to breach the UK’s duties under the European Court of Human Rights.

“So it’s not civil servants who make these decisions, and amending the Civil Service code won’t make any difference,” he said in a post on social media.