Nick Reilly, chief executive of Vauxhall Motors, said that companies such as his would view a UK decision to remain outside the single currency as a negative factor when deciding where to invest. Ken Jackson, leader of the Amalgamated Engineering and Electrical Union, warned that the massive jobs haemorrhage could be much worse if the effect on employment in the financial sector was taken into account.
On the other side of the argument, Business for Sterling, the anti-euro campaign led by Lord Marsh, yesterday wrote to the Prime Minister protesting that it was "unreasonable to expect business to spend billions of pounds preparing for the single currency when the Government's own economic tests for joining have clearly not been met".
Pro-euro Labour MPs are lining up to welcome the Treasury's change-over plan for the euro, due next week, in spite of its failure to provide a clear commitment that Britain will enter the European single currency.
The plan will make it clear that it could take up to two years after a "yes" vote in a referendum before Britain could enter the euro.
Downing Street sources have said the referendum will be delayed until after the next election, making 2003 the most likely entry year.
Speaking at a conference on Europe organised by the AEEU, Mr Reilly said that remaining outside the single currency would cost his company pounds 10m a year. He pointed out that it was now possible to buy a Vauxhall car in Britain by paying in euros, although the company would still be burdened by having to deal in two currencies. He described the situation as a "mess".
"The UK is an integral part of the European Union. We can't pick and choose which suits us and which doesn't," he told the video-conferencing session between the AEEU and the German union IG Metall.