A Labour Government would order every Whitehall department to relocate civil servants outside London, shadow chancellor Ed Balls has announced.
He did not put a figure on the number of officials he wants to move out of the capital, but said that Labour would "go further" than it did during its previous period in power, when a review by Sir Michael Lyons led to more than 20,000 posts being dispersed around the country.
Mr Balls also launched an attack on Chancellor George Osborne for suggesting that new local government powers should only be devolved to cities which agree to adopt elected mayors, and insisted that Labour would make extra powers and funding totalling £30 billion available to city and country regions in all parts of England.
A report on government assets and liabilities produced by Labour frontbencher Chris Leslie as part of the party's "zero-based review" of state spending has found that the proportion of civil service jobs in London has increased since 2010, the shadow chancellor said.
In a speech in Birmingham on the eve of the report's publication, Mr Balls said: "This needs to change if we are to make savings to help get the deficit down and rebalance the economy too.
"So I will ask every government department to draw up a plan for civil service relocation outside London.
"And a Labour Treasury will set an objective for savings over the course of the next decade.
"The last Labour government made progress on moving civil service jobs and government activities outside London.
"Indeed, as Schools Secretary I oversaw the move of the QCA/Ofqual to Coventry.
"But I'm clear that the next Labour government will need to go further.
"And we will."
Mr Osborne said in June that he was ready to offer "serious devolution of powers and budgets" for any city that moved to a new governance model with an elected mayor.
But the shadow chancellor accused him of "short-changing" areas which chose not to stage mayoral elections, which were rejected in a string of cities in referendums two years ago.
"I do not think it is right to short-change city and county regions in the North-East, West and South Yorkshire, the East Midlands or here in the West Midlands by offering up a lesser package of devolution if they do not believe an elected mayor works for them," Mr Balls said.
"To deny the freedoms and resources the Government has granted to Greater Manchester to the Midlands, the North and other parts of England because they will not agree to a Whitehall political blueprint would be unfair and damage growth and job creation.
"Those places which choose to have a combined authority but not to have an elected mayor should not be short-changed by this Government.
"And the next Labour government will not short-change them."
A Conservative spokesman said: " Yet again, Labour have shown that they have no plan to cut the deficit.
"Ed Balls is proposing this as a money saving measure - but can't tell us how much money, if any, it would save.
"No-one should trust Labour when it comes to rebalancing the economy.
"While Labour did next to nothing for three terms and 13 years, it's the Conservatives who are devolving funding and powers in cities like Birmingham with city deals and local growth deals.
"And if Labour were serious about regional development they would also get behind our plan to build a Northern Powerhouse - which devolves real power and serious investment to our great northern cities.
"In short, this is the same old Labour Party: no economic plan, just more borrowing, more taxes and more debt than our children could ever hope to repay."