Rolls-Royce is the latest company to tell workers that a Brexit would be a terrible idea
The company said in a letter to staff that if Britain left the European Union, it would "limit any company's ability to plan and budget for the future," and that the firm would lose out to American competition.
The aero-engineering manufacturer - which has 23,000 employees in the UK - joins telecoms giant BT in communicating directly with its workers to stress the dangers of a Leave vote in the June 23 referendum.
"We have taken the public position that as a company Rolls-Royce believes our customers, suppliers and employees benefit from the UK's membership of the European Union, and that it is in the company's interests to remain a member," says the letter
Rolls-Royce CEO Warren East told the BBC that a planned £65 million ($92 million) engine testing facility could be put in jeopardy if Britain voted to leave, and that it was "all about uncertainty and our position in Europe."
"We have a very interconnected operation around Europe," he said. "We're making investment decisions all the time about where to place various parts of our operation. And uncertainty created by Brexit puts a lot of those decisions on hold, and that pause is something that our US competitors don't have to cope with."
Rolls-Royce is a major player in Britain's European trade, accounting for 1/50th of all British exports, and says it supports about 200,000 jobs across the EU.
Referring to competition with American rivals like GE Aviation and Pratt & Whitney, East told the BBC that "it is like we are running a multi-lap race and with each lap we are giving the competitors a ten-yard head start."
The latest Brexit polls show that the Leave side has surged ahead this week, with a TNS online poll seven points ahead. YouGov and ICM polling show similar gaps. Chancellor George Osborne has suggested there will have to be significant public spending cuts to fill the £30 billion "black hole" if a Brexit goes ahead.