The Deputy Prime Minister said the public should only be given a say if there was a transfer of powers to Brussels – and denied breaking a pre-election promise of a popular vote.
In a long-awaited speech on Friday, Prime Minister David Cameron is expected to announce plans for a referendum on a new settlement with Brussels after the 2015 General Election.
He has rejected calls for an immediate in/out referendum on British membership, which he said would present voters with a "false choice".
But he said it would be right to seek the fresh consent of the British people after negotiating a new settlement for the UK.
Mr Cameron has been caught in an increasingly ill-tempered row within his party, with some Tory backbenchers calling for a public vote on the EU, while business leaders and grandees including Lord Heseltine have warned of the dangers of UK withdrawal.
The issue is also straining relations with the Tories' strongly pro-EU LibDem Coalition colleagues.
Liberal Democrat leader Mr Clegg joined the warnings of business leaders over the impact of exit or the threatened prospect of it.
He said: "I do not think we should do anything to jeopardise our leadership [in Europe] and we certainly should not do anything that would have a chilling effect on jobs in this country.
"We should be very careful at a time when the British economy is still haltingly recovering from the worst economic shock in a generation to create a very high degree and a prolonged period of uncertainty because, in my view, uncertainty is the enemy of growth and jobs, and our priority, in this Government and in the national duty, has got to be to foster growth and jobs.
"If you are an investor investing in the United Kingdom to create jobs here it is unnecessary to create a high degree of uncertainty that might actually chase away that investment and might diminish the number of jobs in this country."
He added: "We do not know yet how the rules are going to be rewritten within the eurozone. We don't know when that will happen, in what way and, crucially, we do not know what that will ask of the United Kingdom.
"We need to give the people of the United Kingdom the reassurance that, if there is a new treaty, and if that new treaty asks new things of the United Kingdom – in other words a transfer of powers from Westminster to Brussels –then we should have a referendum at that point."
The SNP's leader in Westminster, Angus Robertson, said: "Nick Clegg's statement is extremely telling as it shows the Westminster Government knows full well the damage a referendum on the EU would do, but it seems David Cameron is set to press on regardless."
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