Impact of a letter from business chiefs can be 'devastating'

David Cameron received a boost from a number of business leaders in his campaign to keep the UK in the EU Credit: Reuters

Business leaders love a good letter to a newspaper. You may think the strategy tired but it's tried and tested. In the Scottish referendum, in last year's general election, the chief executives and chairmen of Britain's largest companies gathered together and took clear positions in the political debate.

More accurately, they were herded - this process is nothing like as spontaneous as it sounds.

Read more: Business leaders' letter to the Times in full

It is a highly orchestrated affair but the impact of a "letter from business leaders" can be devastating. Last April, when 103 business leaders warned that a Labour government would "threaten jobs and deter investment" Labour scoffed at the idea that ordinary voters care what executives think. With hindsight those closest Ed Miliband have acknowledged it was a highly damaging intervention - one that cemented the perception the party wasn't economically competent.

This time the Times is the recipient (a newspaper that has yet to declare its position on Brexit but surely will at some stage). For the last few days Number 10 has been furiously asking businesses to sign up to a warning that "leaving the EU will put the British economy at risk".

The likes of ASDA, BP, Shell, Centrica, HSBC, Jaguar Land Rover, Rolls Royce, BT, Easyjet, Ryanair, Diageo, BAE Systems, BMW, GSK and Ford all apparently agree that Brexit will broadly "deter investment and threaten jobs" without spelling out the impact on their own businesses.

The boss of ASDA has signed a letter warning of the economic risks of Brexit Credit: PA

Make no mistake, these are big names but there are no new names here. The endorsement of 35 of the FTSE 100 is a pretty good boast (the leave campaign can't claim a single backer) but, in truth, this list doesn't tell us anything we didn't know already.

More interesting are the companies who were asked to sign but haven't. Whitbread and Legal and General have board meetings this week to determine their position. Lloyds Banking Group and Barclays appear curiously conflicted. Royal Bank of Scotland flagged Brexit as a risk to the business last July but doesn't appear on the list.

The boards of Tesco, Sainsbury's, Morrisons and Marks and Spencer have also decided to remain neutral for now. All four are under an obligation to disclose any foreseeable threats to the business to their shareholders, so as it stands Brexit isn't one - although that may change as the opinion polls move in the months to come.

Corporate interest and the national interest are not the same thing. We should however take a very keen interest in how companies in Britain say they will behave if Britain leaves the EU, in as much as it affects the people they employ, the taxes they pay, the prices they charge and the dividends they return to their shareholders (often us, however indirectly).

Business voices are important - the problem is they don't always speak as one. As a rule: the larger the business, the more international its footprint, the more pro-EU it tends to be.

Business leaders who passionately believe Britain can thrive outside the EU do exist and in number. As you read this they are undoubtedly being asked to sign a letter to another newspaper.