LONDON (Reuters) - Britain’s financial sector will be “the servant of industry not the masters of all” if the opposition Labour Party gets into power, its leader Jeremy Corbyn said on Tuesday, accusing bankers of taking the economy hostage.

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Corbyn, a socialist who has won over many voters with promises to renationalise services and increase public spending, has long targeted London’s lucrative financial sector, saying politicians have been in thrall to money-makers for too long.

In a speech to a manufacturers’ conference, Corbyn renewed his pledge to “reprogramme” Britain’s economy if he wins power in an election not due until 2022. He said a Labour government would give businesses clarity over Brexit by repeating its stance on agreeing a customs union with the European Union.

“For a generation, instead of finance serving industry, politicians have served finance. We’ve seen where that ends: the productive economy, our public services and people’s lives being held hostage by a small number of too-big-to-fail banks and casino financial institutions,” he said.

“I simply say ‘no more.’ The next Labour government will be the first in 40 years to stand up for the real economy ... We will take decisions and decisive action to make finance the servant of industry not the masters of all.”

Big business has been cautious towards Labour, with financial services company Morgan Stanley warning investors that Corbyn winning power was a bigger political risk than Brexit.

But they have also started engaging with the party, and Corbyn’s deputy, Labour’s finance policy adviser John McDonnell, took his message that capitalism was living on borrowed time to the global elite at the World Economic Forum in Davos this year.

Any deep mutual understanding looks far off for now.

TheCityUK, Britain’s most powerful financial lobby, was quick to remind Labour of what the sector brought to the country, not only to London. It said the finance industry had created 2.2 million jobs and paid more than 87 billion pounds ($120 billion) in tax towards funding public services.

But in a speech welcomed by many in the audience at the annual conference of the EEF manufacturing group, Corbyn said he was determined to end the spread of finance’s “extractive logic” that prioritised “short-term performance and narrow shareholder value ... over long-run growth and wide economic benefit”.

To applause and some laughter, the 68-year-old leader also called media reports that he had given secrets to a Communist spy in the 1980s “nonsense”, saying he felt “sorry” for some newspapers. Others in his party have gone further, accusing some right-leaning media of mounting a smear campaign against Corbyn.

Asked if he was a spy, he replied: “No.”

(This version of the story corrects to remove reference to jobs outside the capital in paragraph 9.)