The president of the European Commission lashed out at Russia and Ukraine yesterday for their conduct in talks to end a gas dispute, according to The Financial Times.
José Manuel Barroso said he had never witnessed such "really incredible" behaviour before.
As Russian gas flows resumed across Europe, Mr Barroso vented his frustration over the ordeal, accusing both countries of failing to live up to their promises as the European Union worked to broker a truce.
"Let me tell you, frankly, I was very disappointed during these discussions about the way the leadership in these two countries negotiated," Mr Barroso said.
"I will not forget that, and I think European citizens should know that."
His comments came as Russian gas flowed into Slovakia for the first time in two weeks. Bulgaria, another of the 20 countries hit by the gas shut-off, was expected to be receiving full supplies by last night.
Mr Barroso's tone reflected the EU's frustration at a crisis that laid bare its overdependence on Russian gas.
"We must not allow ourselves to be placed in this position again in the future," he said.
Alexander Medvedev, the deputy chief executive of Gazprom, the Russian gas company, hit out at the EU for failing to provide adequate support during the crisis. It called for the adoption of international legislation to prevent similar disputes.
Mr Barroso vowed to use the crisis to win approval from member states to dedicate some ?5bn ($6.5bn, £4.6bn) in unspent EU funds to building energy infrastructure, including grid connections and storage facilities.
He also called for speedy implementation of a strategic energy review that the Commission published in November.
Mr Medvedev said "very strict" payment clauses included in the 10-year gas deal signed by Gazprom and Naftogaz, Ukraine's state gas company, on Monday would prevent the recurrence of disputes.
He said , under the deal, Ukraine would pay an average price below $250 per 1,000 cubic metres for Russian gas this year, with prices fluctuating according to a European formula pegged to world oil prices. European gas prices are expected to average $280 per 1,000 cu m this year.
Ukrainian and European gas prices will converge next year and Gazprom will increase to market levels the fees it pays for use of Ukrainian pipelines that carry 80 per cent of its exports to Europe. Mr Medvedev said an agreement had been reached on settlement of Ukraine's alleged $650m of gas debts, the initial cause of the dispute.
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