Euro-sceptic voices were attempting to "demean" Europe's considerable successes, he said, and were intent on "scoring cheap points by caricaturing our legislation and our institutions", he said.
Mr Santer, speaking in the Netherlands, attempted to veil his attack by criticising Euro-sceptics "everywhere" in the union, in the full knowledge that to intervene directly in the British debate would be viewed by all parties as unacceptable interference in national affairs.
However, Mr Santer, and other European leaders, have clearly been taken aback by the virulence of Britain's anti-European fever, and the timing of Mr Santer's broadside is not a coincidence. There are deep fears among Britain's partners that whichever party wins on 1 May, it will find itself shackled to an anti-European agenda for the foreseeable future.
Britain's partners are particularly afraid that if British anti-Europeanism is whipped up any further, far-reaching plans for EU reform, to be signed at Amsterdam in June, could be scuppered by a British veto.
To block the new treaty would be "catastrophic", warned Mr Santer, because it would end the prospect of enlarging the EU to the east. Greater majority voting and integration must be agreed at Amsterdam if the EU is not to move into "gridlock".
"Those who criticise, do they know what they are talking about? Do they have an equally stimulating alternative? If so what is it?" asked the Commission president. The EU was not devised by "hostile" or "alien" forces but by member governments, he said.
Mr Santer targeted "doom merchants" who present monetary union as a threat to national sovereignty.
Tomorrow the European Commission will publish a report showing that the new euro-zone will be the biggest trading block in the world - bigger than both the dollar and the yen.
The report will highlight more clearly than ever the potential danger to British economic interests if the country stays out of monetary union.Britain is likely to find itself isolated on the world economic stage, the report suggests.
"Let me ask how much sovereignty will be left in a highly integrated world economy with fluctuating exchange rates?
"Rather than being confused by erratic speculation and uncertainty, citizens should be informed about the changes to come, about the advantages which the euro will hold for them, as consumers, savers, workers or tourists.
"I am convinced that the euro will be there from 1999 onwards. Economic and monetary union will not be delayed."
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