Labour helped to create an "unfair tax system" when it was in power, the Shadow Chancellor has said.

The party will be more "radical" if it takes power in 2020 than it was when it created the NHS, John McDonnell declared.

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At a conference in central London, he said too many institutions at the heart of the British economy were "not fit for purpose".

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The party will revive plans for rent controls and urge councils to follow the lead of areas like Manchester to offer cheap, local authority-backed mortgages, Mr McDonnell said.

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"Labour would make it a mission to ensure families and young people on ordinary incomes aren't locked out of home-ownership as they are under the Tories, he said.

The shadow chancellor also used the conference to announce plans for a mayors' economic forum to allow the elected local leaders to share ideas along with a new economic and innovation forum to bring together businesses, unions and government.

Labour under Tony Blair and Gordon Brown did not do enough to tackle tax dodging, the left-winger said.

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"The old rules meant the last Labour government relied too heavily on tax revenues from financial services, and too heavily on off-balance sheet spending through the Private Finance Initiative," he said.

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"It didn't do enough to clamp down on tax evasion and avoidance. It helped create an unfair tax system."

Mr McDonnell said there was a "fixation" in big business with shareholder value and criticised corporations for "hoarding" cash and paying chief executives "obscene" amounts.

Labour last year launched a review into the Treasury, HMRC and Bank of England that will lead to reforms in the way they operate if the party takes power, he said.

It will "rewrite the rules" of the way the economy functions, he insisted.

HMRC has too often let major corporations "off the hook" over their taxes and "serious questions have to be raised about its management".

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The Bank of England's current architecture was established under the Blair/Brown government and there are "legitimate questions as to whether the Monetary Policy Committee's remit still fits changed circumstances", he said.

He added: "And then at the heart of economic policymaking in Britain sits the Treasury. Its powers, already expansive under Gordon Brown, have grown hugely under Osborne. "

It dominates not just economic policy, but the whole of domestic policymaking in Whitehall.

"Its staff are talented and dedicated. But, time and again, it has faced serious questions about its own role."