Media playback is unsupported on your device Media caption Brexit 'could lead to 4,000 JP Morgan job losses'

JP Morgan may cut up to 4,000 UK jobs if there is a vote to leave the European Union, its chief executive has warned.

Jamie Dimon said that Brexit would "be a terrible deal" for the UK economy.

He was speaking alongside Chancellor George Osborne at JP Morgan's base in Bournemouth, where the US bank has 4,000 staff.

Leave campaign spokesman, Steve Baker MP, said it was time for the 'In' campaign to engage in an honest debate.

Mr Dimon said: "After a Brexit we cannot do it all here and we will have to start planning for that. I don't know if it means 1,000 jobs, 2,000 jobs - it could be many as 4,000, and they will be jobs all around the UK."

"If the EU says anybody who does business as a bank with an EU company has to be based in the EU, you're talking about three or four thousand JPM [JP Morgan] jobs."

JP Morgan employs 16,000 people in the UK in Basingstoke, Edinburgh, Glasgow and Swindon as well as London, which is the bank's European headquarters.

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The bank is the biggest private sector employer in Dorset, where it has technology and operational processing. Its links with the UK date back to the mid-19th century.

In an interview with the BBC, Mr Dimon said that if the UK voted to leave the EU the "real work and worry" would start on 24 June.

"We will set up real task teams, war rooms etc, to start doing the real heavy work... we are going to start planning for the worst. I have to - if you were my board you would say: 'Are you prepared if the outcome is a really bad one?'."

'Deception'

Mr Osborne said that the Leave campaign must stop telling voters that jobs will be secure if Britain leaves the EU.

"Let's end this deception that somehow if you quit the EU jobs won't be at risk," the chancellor said. "Our analysis shows in the services sector alone 400,000 jobs could be at risk."

Steve Baker MP, a Leave campaigner, said: "The British people will not be bullied into voting to hand more money and more power to Brussels by someone whose bonus would make even some eurocrat's eyes water and whose bank helped crash the economy.

"It's time for the 'In' campaign to engage in an honest debate, not make unsubstantiated and illogical threats which are the real danger to our economy."

Analysis: Simon Jack, BBC business editor

As a member of the EU, the UK serves as a base for foreign owned banks to sell services to any other country in the EU. On Brexit, that so-called "passport" for the selling of financial services may have to be renegotiated.

Other EU financial centres would certainly welcome the chance to prise lucrative business away from London.

Some, including one of his own former lieutenants (pro-remain Barclays chief executive Jes Staley) say London's crown as Europe's most important financial centre, would not slip even if there was a short-term impact on the UK economy.