Britain and Germany piled the pressure on Moscow and Kiev today to settle their gas row and resume normal supplies to all members of the European Union as the energy crisis entered a critical phase.

Millions of homes in Central and Eastern Europe have been left without fuel, factories have shut down and school holidays extended indefinitely because Russian gas is not reaching its customers. Discontent over the Big Chill fed into anti-government riots this week in Bulgaria, one of the countries most heavilly dependent on Gazprom deliveries.

José Manuel Barroso, president of the European Commision, is urging European companies to take Russia and Ukraine to court; the Kremlin, meanwhile, has been trying to organise an international gas summit in Moscow.

"It is our joint demand that gas is again delivered to Europe," said Angela Merkel, the German Chancellor, after a breakfast meeting in Berlin with Gordon Brown, the British Prime Minister, "and we demand that both Russia and Ukraine create the appropriate conditions."

Mrs Merkel warned Moscow that Europe would lose faith in it as a supplier of natural gas if it failed to settle its differences with Ukraine. The German leader said that she would be driving the point home when Vladimir Putin, the Russian Prime Minister, comes to Berlin tomorrow. But German leverage is not particularly strong: it is locked into 30-year gas delivery contracts from Russia.

"I believe there is a danger that Russia will lose a chunk of its credibility if there is a long interruption of gas deliveries," Mrs Merkel said.

Mr Brown also hinted that the arguments over the reliability of Russian gas supplies would speed the search for other sources of fuel.

"The events of the past week in Russia and Ukraine have reinforced to the world the need to diversify energy supplies," Mr Brown said. This was essential, he said, "not just because of energy security but also adapting to climate change and securing the affordability of energy in the future".

Mr Brown's trip to Berlin was chiefly to prepare the ground for the April summit in London of the G20 which is supposed to build a new financial architecture for the world, with greater monitoring of the banking system. But both leaders found themselves worrying about a possible EU crisis generated by the fall-out between Russia and Ukraine.

Mr Putin has held talks this week with the prime ministers of Slovakia and Bulgaria — both of whom have to demonstrate to their unhappy electorates that they are pulling out all the stops — and thus sapped a common European Union position. The fact is, some countries such as Britain and France are largely untouched by the Russian gas blockage; other countries like Germany, though heavilly dependent on Russia do have large stockpiles; and others, such as Bulgaria, can be brought to their knees.

The question then arises how the big less vulnerable EU states can express solidarity with the weaker states —and what happens on the streets when that solidarity looks at best luke-warm.

For the time being Mr Putin is trying to persuade the big EU states to align with Moscow against Kiev. In an interview with German state television before coming to Berlin, he made clear that the best solution for Moscow would be if Ukraine privatised the gas transit pipelines.

That, he says, would remove the Ukranian state monopoly and depoliticise an essentially commercial argument about pricing and unpaid debts to Gazprom. Ukraine believes that the Russians would try to secure the gas transit by entering the privatisation process and buying up companies.

The Russian Prime Minister has another goal during his German visit tomorrow: to convince ordinary Germans that he is a nice guy, and that Gazprom is no long term threat. To that end, he will be attending the renowned Dresden Semper Opera ball — a grand gala dance in the same city where he once served as the head of the KGB station.

Times Recommends

• Mandela’s tribe threatens President Zuma
• The French empire strikes back
• Wife of cheating governor exacts a political revenge