In announcing the crisis was over, commission president Jose Manuel Barroso said, “It’s very difficult to welcome something that should not have happened in the first place”.

This was not the first time tensions between Ukraine and Russia squeezed EU gas supplies. Similar disputes in recent years have shown the need to reduce the EU’s reliance on foreign energy, one of the commission’s top priorities.

The president said the EU must diversify its energy supplies and build up strategic stocks. And he urged European leaders to rapidly agree to the commission’s recommendations to use €5bn in unspent EU funds to build energy infrastructure. Measures to develop energy security and tackle climate change are mutually reinforcing – energy efficiency and renewables are as important as safe energy supplies.

Russia cut off supplies that flow through neighbouring Ukraine in a dispute over the terms of a new supply and transit contract. The Russian and Ukrainian prime ministers reached agreement on a new contract over the weekend and the deal was signed on 19 January.

The Commission and the Czech presidency of the EU held many talks with Russian and Ukrainian leaders during the standoff. At one point, the EU brokered an agreement to resume natural gas supplies to Europe under the supervision of EU monitors, but the two countries failed to honour it.

The monitors, who remain in place in the two countries, have confirmed the gas has begun flowing.

The EU gets about a quarter of its natural gas from Russia, mostly through pipelines in Ukraine. The level of dependence varies widely though, with some countries relying on Russia for nearly all their gas. The EU countries most affected by the cut in gas supplies were Slovakia, Czech Republic, Bulgaria, Romania, Greece, Austria and Hungary.