Russia allowed the rouble to fall to its lowest level against the dollar in six years on Wednesday as it speeded up a step-by-step devaluation, conducting the third drop in the currency’s value in four days.

The rouble fell to Rs31.76 to the dollar, its weakest since February 2003. The move came as pressure mounted on the central bank to accelerate devaluation of the currency after it was disclosed this week Russia had spent a record $74bn in hard currency reserves in December defending the rouble.