Frantic efforts to restore gas supplies to millions of European consumers failed yesterday after Russia refused to turn the pipeline back on in its showdown with Ukraine.

A European Union plan to send monitors to both countries, agreed in principle by Moscow and Kiev as a way of breaking the deadlock between them, faltered at the 11th hour when Russia demanded that its own inspectors should be sent to Ukraine alongside independent experts. Last night the EU decided to send its monitors to Ukraine anyway, in the hope of persuading Russia to re-open the taps.

The row has left 12 countries without deliveries in freezing temperatures and meant hundreds of schools and factories have closed to conserve fuel. Hundreds of thousands of people across the Balkans, the worst-affected region, found themselves without heating and some hospitals were forced to close in Serbia as temperatures dipped below minus 10C (14F).

A senior US diplomat warned that Nato might have to intervene to help alliance members such as Bulgaria and Romania if the crisis drags on. “There is a commercial dispute at the heart of this, but this also has political overtones [becasue] we have seen Russia over time using such events to gain political leverage,” Kurt Volker, the US Ambassador to Nato, said.

“If this persists, I think Nato will have to think how to assist allies who suffer.”

Russia and Ukraine continued to blame each other while simultaneously proclaiming their readiness to end the row, which has grown into a devastating fuel shortage for Europe in one of the coldest winters for years.

Four-fifths of Russian gas for Europe should arrive through Ukraine’s pipeline network but Gazprom, the Russian state fuel company, turned off all supplies on Wednesday in an increasingly bitter row over payments that began on New Year’s Day.

Russia had decided to punish Ukraine by cutting its gas and later accused it of stealing supplies that were intended for Europe.

After a day in Brussels of complex, and at times chaotic negotiations, Alexei Miller, Gazprom’s CEO, objected to the plan to send European monitors to Ukraine to ensure that the country would not siphon off supplies destined for Europe.

Despite announcing his support earlier in the day for the scheme, he insisted that Russians should be part of the monitoring teams — a demand that would first have to be agreed by Ukraine.

EU officials had hoped that placing monitors in Russia and Ukraine to check the gas flow would ensure that both countries kept their promise to pump gas to Europe. Gazprom’s last-minute demands scuppered the deal and came as a bitter disappointment to negotiators.

Andris Piebalgs, the EU Energy Commissioner, said: “It is very clear that the citizens in Europe are suffering a lot. My goal was to be able to name the moment when gas flows would come to Europe. However, I cannot name a date or a time.”

Mr Piebalgs said a dozen EU monitors would be sent to Ukraine today so that they would be able to check supplies as soon as they resumed.European foreign ministers, meeting in Prague, accused Russia and Ukraine of “showing insufficient determination to solve the problem”.

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