Among them is Sir Richard Branson, the pro-EU Virgin billionaire, who is today launching his own campaign keep Britain in Europe by warning that he is “deeply concerned about the impact of leaving”, reports The Telegraph.
His intervention is the first in what is likely to be a series of pleas by business leaders – for and against EU membership – to voters before ballot boxes open on Thursday.
It is thought that a host of FTSE 100 chief executives and chairmen are putting their name to a letter encouraging the UK to stay in the EU, which could be published today.
They will warn that a so-called Brexit would likely result in an “economic shock” that would be most damaging to small firms.
Similarly, pro-Leave business leaders, who include J D Wetherspoon founder Tim Martin, are also expected to make final attempts to convince Britons to quit the EU in the last days before the referendum.
The City is bracing for dramatic market swings whatever the outcome of the referendum, with a number of banks ensuring they have foreign exchange traders at their desks overnight to deal with volatile currencies as the result comes through.
Virgin founder Sir Richard, who has long been an strong supporter of the Remain campaign, said: “As an entrepreneur I have been known for taking risks throughout my career but leaving the European Union is not one of the risks I would want the UK to take.”
The billionaire, whose home is Necker Island in the Caribbean, added: “Although I’ve been living in the British Virgin Islands for some time now, I have never stopped caring passionately about the UK and its great people.”
This newspaper reported last week that the tycoon was preparing to intervene in the debate, after one of his companies registered with the Electoral Commission to allow it spend heavily on campaigning.
It comes as a survey from recruiters Per Ardua shows that finance firms are not panicked by the prospect of Brexit.
The study of 35 City chairmen and chief executives found that 88pc want to remain in the EU, but that does not mean they are worried by the idea of leaving – despite opinion polls remaining finely balanced ahead of the referendum, 88pc also said the have not held back from making investments ahead of the vote.
“The discovery that most financial services companies haven’t been holding off making investments ahead of the referendum flies in the face of received wisdom and the many polls conducted over the last three to six months which have suggested that non-financial services businesses are holding off investments until the second half of this year,” said Per Ardua’s Simon Hearn. “Clearly this is not the case for financial services firms.”
Meanwhile, steel producer Celsa, which has a plant in Cardiff, has warned that Britain’s troubled steel sector would feel further pain if the UK votes to leave the EU.
In a letter to its almost 800 staff, the company said while it was up to them to decide how to vote in Thursday’s referendum, it felt it had a “ responsibility to tell [them] about the risks that leaving the EU poses”.
Chris Hagg, Celsa’s external affairs director, said that “if Britain were to leave the EU, the UK would have less influence on efforts to support our industry and put an end to anti-competitive practices around the world”.
EDF Energy, which has almost 14,000 UK staff, also wrote to its employees, saying that Brexit could mean “break it” for the EU.
Vincent de Rivaz, chief executive of the French-owned company which is due to build Britain’s much delayed new nuclear power station at Hinkley Point, spelled out what he saw as the advantages of staying in the EU, but Vote Leave called the move “unsurprising” in light of EDF’s ownership.
The automotive sector also warned again that a vote to leave could “jeopardise” jobs and investment in the industry, which directly employs 160,000 in manufacturing, and supports a total of 800,000 jobs in the wider sector.
According to the Society of Motor Manufacturers and Traders, the UK vehicle industry has an annual turnover of £60.5bn and this could be put at risk by Britain leaving the EU.
Mike Hawes, chief executive of the trade body, said: “We want this success to continue rather than jeopardise it by increasing costs, making our trading relationships uncertain and creating new barriers to our single biggest and most important market, Europe. Remaining will allow the UK to retain the influence on which the unique and successful UK automotive sector depends.”