Airbus has been accused of "bullying voters" after the aerospace and defence giant said it would reconsider its investment in the UK if the country elected to leave the EU.
Paul Kahn, president of Airbus UK, which has around 16,000 employees in Britain, warned that the country would be less competitive if its people voted to leave the EU in the forthcoming referendum and that, by remaining a member, it was best placed to compete for international investment within the 28-member bloc.
The added bureaucracy of no longer belonging to the trade bloc would be a hindrance, he said. "Waste will go up. Non-value added will go up. If it takes one extra form to be filled in, or one day's delay, that is something our customers will not pay for," he told the Financial Times.
The intervention prompted one Conservative MEP to claim that Kahn was "bullying voters" with his comments.
David Campbell Bannerman, who represents the East of England in the European Parliament, said on Twitter: "Airbus without wings is a bus: which are very specialist and UK built. This clumsy attempt to bully UK voters won't wash."
Airbus has been joined by the likes of the Confederation of British Industry (CBI) and the Institute of Directors (IoD) in warning of a Brexit.
Simon Walker, the director-general of the IoD, told IBTimes UK that a withdrawal from the political and economic union would be "disastrous".
"We are in favour of staying in a reformed EU, there's no doubt about that. Britain should be the leading force for deregulation inside the EU," he said.
The Out campaign was bolstered earlier in the week after the chairman of construction equipment giant JCB backed an exit from Europe.
Lord Bamford, whose family have donated millions of pounds to the Tories, told the BBC: "We are the fifth or sixth largest economy in the world anyhow, so we could exist on our own, quite peacefully and quite sensibly.
"We could negotiate as our own country, rather than being a 28th nation in Brussels, which is what we are at the moment."
David Cameron, who is expected to campaign for an "In" vote, will table his EU referendum bill a day after the Queen's Speech next week on 28 May. The draft legislation will be the first legal step towards the historic vote scheduled for the end of 2017.