A sale by BP of its 50 percent stake in Russian venture TNK-BP now could be a bad move, Liam Halligan, chief economist at Prosperity Capital Management, told CNBC’s “Squawk Box Europe.”

On Friday, BP said it had received interest in the stake and would pursue the sale. A successful sale of — Russia's third-largest oil firm estimated to be worth $30 billion — to the state would boost government control of the country's oil production to over 50 percent.