The director general of the Confederation of British Industry has said Britain must make its decision on the euro within the next year or so and "get on with its life".
Mr Digby Jones is calling on the British government to end "delay and prevarication" on the issue.
He is backed by the general secretary of the Trades Union Congress Mr John Monks, who says it is time to "face up" to policy changes.
Both men predict that manufacturing industry faces a "challenging" year, with Mr Jones saying uncertainty about Britain's membership of the euro inevitably has an "impact on investment decisions".
He told BBC Radio 4: "Britain has got to be shown to make its decision and get on with its life because I'm very concerned as we face, as Europe, a global slowdown in a competitive world, economic reform in Europe is not happening.
"Britain cannot really influence that if we are a country member and we have got to show where we are actually standing and, over the next year or so, actually come to a decision one way or the other."
Mr Jones added: "It is the delay and the prevarication which causes the problem."
Mr Monks said: "I think it is important, looking at the year ahead, while people do get used to the euro that, actually, we do start facing up to the big policy choices before this country, which is are we going to join a major trading area on our doorstep with its single currency or are we going in a sense to be half in, half out?
"Today I am asking the government to move forward on it and to step up the preparation, otherwise we are in a sense going to put it off and put if off... and then we'll be talking about the next election rather than perhaps next year."
Mr Monks said manufacturing faced a "bleak outlook", and predicted a rise in unemployment next year.
PA