Liz Truss has promised a “war on Whitehall waste”, cutting Civil Service time off, ending national pay deals and scrapping jobs aimed at increasing inclusion and diversity in the public sector.

The Foreign Secretary claims her plans would save £11 billion and tackle left-wing “groupthink” within the Civil Service.

The bulk of the savings – some £8.8 billion – would come from paying workers living in cheaper areas of the country less than counterparts in places like London and the South East where the cost of living is higher.

Her proposals met with a furious response from a major civil service union, which vowed to oppose her plans “every step of the way”.

I have shown in my time in Government that I’m prepared to take on the Whitehall orthodoxy and get things done

Ms Truss said: “As prime minister I will run a leaner, more efficient, more focused Whitehall that prioritises the things that really matter to people and is laser-focused on frontline services.

“There is too much bureaucracy and stale groupthink in Whitehall. If I make it into Downing Street, I will put an end to that and run a government that focuses relentlessly on delivering for the British public, and offer value to hard-working taxpayers.

“I have shown in my time in Government that I’m prepared to take on the Whitehall orthodoxy and get things done.

“The British people can trust me to deliver on my promises and tackle the cost of living immediately.”

The Truss campaign argued that because Civil Service pay is negotiated at a national level, no account is taken of the regional cost of living.

By introducing regional boards, civil servants’ pay can be adjusted in line with the actual areas where they work, saving the taxpayer billions but also ensuring private employers are not “crowded out” by higher public sector wages.

The savings could be enhanced by moving more civil servants out of London.

Around £2 billion would be saved by bringing the average Civil Service leave entitlement down from 27 days to the 25 found in the manufacturing and private services sectors.

Scrapping Whitehall diversity officers would save around £12 million a year – Ms Truss’s campaign said there are at least 326 of the roles in government departments.

Facility time, under which trade union representatives receive paid time off to focus on union work, would be banned – as would allowing the use of grants, offices and equipment – saving up to £137 million, the Truss campaign said.

The package of measures set out by Ms Truss are likely to meet fierce resistance from Civil Service unions if she tries to implement them from No 10.

A campaign source said: “Liz is a low-tax, small state Conservative with a distrust of big government. She will shake up Whitehall and take the radical steps required to tackle the waste and inefficiencies that lie at the heart of government.

This wannabe prime minister is stuck in the past, fighting old battles, and promising a race to the bottom on public sector workers’ pay and rights

“She will make sure every single official knows their job about delivering the pledges made in the 2019 manifesto and the things that the public care about.”

Mark Serwotka, general secretary of the PCS union, said: “If Liz Truss is elected, and if she tries to go ahead with these proposals, she’ll face opposition every step of the way.

“Civil servants are not a political tool to be used and abused for one person’s ambition; they are the hard-working people who keep the country running, day in day out, and they deserve respect.”

Mike Clancy, general secretary of Prospect union, said: “Liz Truss has spent the last few weeks trashing the record of her own Government. Judging by this vacuous attempt to garner headlines friendly to her selectorate, she plans more of the same economically illiterate and insulting ideological nonsense that this Government has been churning out in recent years.”

Deputy Labour leader Angela Rayner condemned Ms Truss’s plans, saying: “This wannabe prime minister is stuck in the past, fighting old battles, and promising a race to the bottom on public sector workers’ pay and rights.

“Her ‘tailored’ pay plans would level down the pay of northerners, worsening the divide which already exists. This out-of-touch Government’s commitment to levelling up is dead.”