"If member states put more allowances into the market than are needed to cover real emissions, the scheme will become pointless and it will be difficult to meet our Kyoto targets," commissioner Stavros Dimas told journalists in Luxembourg.

Member states are in the process of notifying the European Commission how many emissions allowances they will hand out to industrial polluters over the 2008-2012 period, the second phase of the landmark scheme.

The allowances are the cornerstone of the quota trading system which was launched at the beginning of 2005 to help member states meet their greenhouse gas emissions targets under the Kyoto Protocol.

The aim of the scheme is to encourage industrial polluters to reduce their emissions by allowing them to sell any unused quotas to companies that have surpassed their allowances.

However, Dimas said that member states that had filed their plans with the commission so far had allocated more emissions permits than polluters would probably emit, based on real emissions from 2005.

"I have to say that many of the national allocation plans that we received so far do not seem to take sufficient account of the real level of emissions from installations," he said.

"Much to my regret, taking together the first 17 national allocation plans that have been notified to us proposing emissions caps, that is about 15 percent above the emissions levels in those cases," Dimas added.

The scheme's credibility took a beating earlier this year when it emerged in May that polluters did not use all of the permits allocated to them during a 2005-2007 trial phase, causing the market price for permits to plunge.

Environmental groups seized on the discrepancy as evidence that EU governments had attributed too many allowances to companies and undermined the programme.

Earlier this month, the EU's executive commission launched proceedings against eight members for failing to send the allocation plans for the second 2008-2012 phase.

In a first step towards legal action, the commission sent warning letters to Austria, Czech Republic, Denmark, Hungary, Italy, Portugal, Slovenia and Spain for ignoring the deadline.

With member states ignoring the deadline or offering more permits than needed, Dimas reiterated a warning that he would go "tough" on countries that did not take the plans seriously.

"I've said repeatedly that the commission will be tough but fair in our evaluations of the national allocation plans," he said. "It is clear that we will need to be."