JP Morgan is preparing to make a substantial donation to the campaign to keep Britain's European Union membership in a move that will extend Wall Street's involvement in the debate.
Sky News has learnt that JP Morgan will join its bitter rival Goldman Sachs by writing a cheque for hundreds of thousands of pounds to Britain Stronger in Europe.
Sources said that JP Morgan's financial contribution was in the process of being finalised and was expected to be made in the coming days.
:: Goldman To Help Bankroll EU 'In' Campaign
The precise sum involved was unclear on Thursday, and JP Morgan declined to comment.
Tony Blair, the former Prime Minister, is an adviser to JP Morgan and a staunch supporter of the EU, although it is not thought that he was involved in the decision to donate funds to BSiE.
Chaired by Lord Rose, the former Marks & Spencer boss, the pro-EU campaign group has embarked on a broad fundraising effort, with a referendum potentially just five months away.
The involvement of Wall Street firms - with Bank of America Merrill Lynch and Morgan Stanley also understood to have been courted - reflects deepening anxiety among senior bankers about the potential economic disruption that they believe a British exit from the EU would cause.
Executives' concerns about the impact of Brexit relate to both the likely end to the UK's ability to access the EU's single market in financial services, and the wider corporate uncertainty that many financiers believe would ensue.
However, the backing of firms such as Goldman and JP Morgan may stoke accusations of a 'takeover' of the campaign by financiers focused on protecting their firms' interests.
Pro-Brexit campaigners argue that leaving the EU would allow Britain to negotiate more advantageous trade deals, and that the City would be largely unaffected.
In addition to Lord Rose, Britain Stronger In Europe's board includes Baroness Brady, one of the stars of The Apprentice; Brendan Barber, the former secretary-general of the Trades Union Congress; and Lord Mandelson, the former Business Secretary.
A number of high-profile City figures have adopted the opposing position, including Crispin Odey, the hedge fund manager, and Helena Morrissey, the boss of Newton Investment Management, who believes the risks of Brexit have been overstated.
Alongside market turmoil prompted by the oil price and China's economic slowdown, the question of Britain's EU membership is one of the biggest talking points at this year's World Economic Forum in Davos.
Sky News revealed on Wednesday that David Cameron, who is in Davos, has urged business leaders to publicly back his reform negotiations ahead of next month's crucial EU summit.
He will hold talks with senior executives from British companies in the Swiss mountain resort on Thursday.
Source: http://news.sky.com/story/1626855/jp-morgan-hands-cash-to-pro-eu-campaign