French foreign minister says £1bn contract for two high-tech Mistral warships could be blocked if situation escalates

France might cancel a controversial deal to sell two state-of-the-art warships to Russia but only if Britain also acted against Russian oligarchs in London, according to the French foreign minister.

Speaking after Russian president Vladimir Putin approved a draft bill for the annexation of Crimea before the parliament in Moscow, Laurent Fabius warned he "could envisage" blocking the €1.2bn (£1bn) sale.

France is due to deliver two high-tech Mistral warships to Russia. The first, christened the Vladivostok, has already undergone sea trials from the port of Saint-Nazaire. A second, called the Sevastopol, is due to be completed by the end of next year.

"If Putin continues doing what he is doing we could envisage cancelling the sales," Fabius told TF1 television on Tuesday. "This would be part of a third level of sanctions. For the moment we are at the second level.

"But we will ask others, and I'm thinking namely the British, to do the same with the assets of the Russian oligarchs in London. Sanctions have to be shouldered by everyone."

Fabius admitted cancelling the contracts would be "negative for the French" - and his comments drew swift criticism from Russia's deputy prime minister, Dmitry Rogozin.

"France is starting to undermine confidence in it as a reliable provider in the very sensitive sector of military and technical co-operation," Rogozin, who oversees the military sector, said on Twitter.

Fabius's comments mark an apparent change of tack by Paris, which had previously ruled out blocking the deal. Even as the Crimea crisis erupted, the French president, François Hollande, insisted the contract would be honoured. Asked if the deal would be cancelled last Thursday, Fabius replied: "We'd rather not reach that point."

The deal, the first between Russia and a Nato country, had already raised deep misgivings among France's allies when it was signed by former centre-right president Nicolas Sarkozy in 2011, just three years after the Russian invasion of Georgia in the Caucasus.

The Mistral – a 180-metre, 22,000-ton vessel – is capable of carrying 16 helicopters, four landing craft, 60 armoured vehicles, 13 battle tanks and between 450 and 700 soldiers for up to six months and will give the ageing Russian naval fleet a new lease of life. The vessel is known by the French navy as a military "Swiss army knife" for its multiple attack capabilities and use as a command centre, hospital as well as helicopter and troop carrier. The Russians have taken an option on a further two Mistral warships.

In 2008, Commander Vladimir Vysotsky, head of the Russian navy, said his forces would have been victorious in Georgia "in just 40 minutes" if his ageing Black Sea fleet had been equipped with the French warships.

Shortly afterwards, Putin said during a visit to Paris: "I can assure you that if we purchase this armament, we will use it wherever deemed necessary."

At the time of the deal both Washington and several of Russia's neighbours, including the three Baltic states, criticised Paris's decision to sell the warships to Moscow, which was still referring to Nato as an enemy.

Republican senators wrote to the French ambassador in Washington complaining the sale was inappropriate because it would suggest France approved of Russia's "increasingly aggressive and illegal" conduct. In 2010, former American defence secretary Robert Gates made no secret about the US's disapproval of the Mistral deal.

"Yes, we [the US and the French] did discuss it. We had a good and thorough exchange of views. I will leave it at that," Gates said.

France, however, was jubilant with the Elysée declaring: "France's naval industry has won." Sarkozy also rejected criticism at the time. "The cold war is finished … we have to consider Russia as a friend and have to work with her to build a vast area of security and prosperity together," he said.

France has insisted it is not fitting the ships with weapons technology. However, Moscow has said the deal includes the technology from France to produce the Mistral's command and control system itself.