The Bank of England has warned that 10,000 jobs could leave the City on “day one” after the UK leaves the EU.

Sam Woods, a deputy governor of the Bank, also admitted that forecasts of 75,000 job losses over the long-term were “plausible” at an appearance before peers on the Lords EU financial affairs sub-committee on Wednesday.

Woods runs the regulatory arm of the Bank and based his estimate of 10,000 jobs on responses he received from 400 banks and financial firms required to provide him with their contingency plans for a hard Brexit.

He has been reviewing the plans since July and said some were being put in place – with banks reserving school places and hiring office space – but that this process would get under way “in earnest” in the first quarter of 2018.

The estimate of 75,000 job losses was made by consultancy Oliver Wyman, and based on the assumption that the UK would be left to rely on World Trade Organisation rules with no transition period after March 2019, when the UK leaves the EU.

Under this scenario, £10bn of tax revenue might also be lost, it said. The 75,000 estimate includes the knock-on effect of fewer City jobs to other parts of the economy.

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Woods said this was not a Bank of England estimate, but described it as being within a plausible range of job losses that would happen in the long term if the UK left the EU without a trade deal.

He said the actual number was a “moving feast” and that the initial impact of about 10,000 roles amounted to 2% of the total employed in bank and insurance jobs, or less than 1% of financial services jobs.

Woods has previously called on the government to agree a transition deal by Christmas to give firms more certainty about Brexit and reduce risks to the financial system that may arise as companies adjust their business models to continue to be able to access the remaining 27 EU countries.

He told peers this was also important because the Bank of England had to make arrangements for EU banks and financial services firms that needed to be authorised to allow them to continue operating in the UK after Brexit.

“We will need to get going,” Woods said, warning that the changes being made would increase complexity for firms.

He was speaking the day after Andrew Bailey, the chief executive of the Financial Conduct Authority, told MPs that banks could start to make irreversible moves to transfer staff from London to rival cities in the EU unless there was clarity over Brexit by the end of the year.

Goldman Sachs has begun to implement contingency plans by taking the top eight floors of a 37-storey block under construction in Frankfurt, even though it is building a new European headquarters in London.

The US investment bank employs 6,000 staff in London and its chief executive Lloyd Blankfein tweeted this week that the decision on how many staff to keep in London was “so much outside our control”.

Political uncertainty was also mentioned by Jes Staley, chief executive of Barclays, at an event in Westminster on Wednesday. “Like all of us, we are in sway to the desires and wishes of the political bodies and I have no idea how that will go,” Staley said, according to Reuters. Barclays has said it will expand its Dublin operations to cope with Brexit.