Bank of England staff have voted to hold their first strike in more than 50 years in a push for higher pay, a union said on Monday, adding to pressure for an end to tight controls on public sector wages in Britain.

Unite, Britain's biggest union, said maintenance and security staff at the 323-year-old institution would strike for four days from July 31 after they were awarded a 1 percent pay rise.

That period coincides with the bank's next monetary policy meeting.

British Prime Minister Theresa May has come under increasing pressure from members of parliament to end a below-inflation 1 percent cap on public sector pay rises that have been in place since 2013 as part of efforts to cut government spending.

Although this cap does not apply to the independent Bank of England, it operates in an environment of pay restraint for public officials. Strike action would be potentially embarrassing for an institution whose policymakers have focussed heavily on the prospects for wage growth.

The Bank, which employs some 3,600 people, said Unite balloted around 2 percent of its workforce.

"Should the strike go ahead, the Bank has plans in place so that all sites can continue to operate effectively. We will continue to have discussions with Unite and hope that there will be a positive outcome," the BoE said in a statement.

Unite said some Bank staff earned less than 20,000 pounds ($25,700) a year, so a 1 percent pay rise would potentially leave them facing financial hardship.

The union called on Bank of England Governor Mark Carney to intervene, saying it would look to escalate the action if the dispute was not settled.

Workers in Britain have suffered a protracted hit to their spending power after the global financial crisis due to inflation rising faster than wages for most of the past decade.

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