Trussonomics was dropped after Simon Case told the prime minister it was causing havoc in the market.

Liz Truss has announced tax breaks in her sole budget as prime minister. Photo: AP

Lise Truss backed away from the tax cut after the head of the civil service warned him it was causing market chaos, it surfaced.

Simon Case, cabinet secretary, wrote a memorandum to the former prime minister a minister urging her to drop the measures announced in last year's mini-budget.

The statements, published by The Spectator magazine, will rekindle the debate about how much influence Whitehall tangerines have to dictate government policy.

It comes after civil servants at the Home Office threatened to go on strike instead of implementing Downing Street's migration policy.

Ms Truss announced a series of tax breaks in her sole budget as prime minister last September. including the abolition of the 45p income tax rate.

But the announcement, which was not accompanied by an OBR forecast or any money-raising measures such as spending cuts, sent markets into chaos.

Government borrowing costs rose by a record amount in one day as investors sold off British assets. fearing that deposits would not be available.

Simon Case has been heading the civil service since 2020. Photo: GETTY IMAGES

Ms. Truss was forced to fire Mr. Kwarteng just three weeks later and bring in Jeremy Hunt, who immediately reversed almost all measures.

Mr. Case's involvement in dealing the death blow to Trussonomics will further fuel the battle between the Tories and the public service.

Tensions have escalated over threats from the public and commercial services union to lead a strike by Home Office employees and border control.

It says demoralized workers fear they will be forced to violate international law by pursuing a migration policy similar to Rwanda's plan.

Jacob Rees-Mogg, a former business secretary, said «a civil servant who refuses to be a legitimate politician should resign or be fired.»

Priity Patel, a former home secretary, added that Whitehall officials should «respect the policies and laws of a democratically elected government.»

Who is Simon Case?

Special advisers working for the government also complained to The Spectator that government employees are «slowing down» to kill policies they don't like.

This included tactics where «officials cut time when they'll know a reshuffle is coming,» one former adviser to the minister told the magazine.

The former cabinet minister described how, when they tried to make changes, they were told, «Maybe it's the minister's policy.» but it's not a department.»

Senior Tories have also faced public service in recent weeks due to their role in the Partygate investigation into Boris Johnson.