Committing money to the IMF, as the Chancellor has done, is not the same as spending it. The money will only be used in the event of a financial crisis in which IMF members need bailing out, and is refundable. The IMF head Christine Lagarde said:
This signals the strong resolve of the international community to secure global financial stability and put the world economic recovery on a sounder footing. These resources are being made available for crisis prevention and resolution and to meet the potential financing needs of all IMF members. They will be drawn only if they are needed, and if drawn, will be refunded with interest.