Labour has been accused of double standards for amending legislation to allow world leaders to use smoking rooms during the G20 economic conference.
Dozens of heads of state, politicians and diplomats will be meeting at the Excel Exhibition Centre in Docklands, London, next month.
It is believed that laws have been changed to get around the smoking ban and provide specialist rooms that the visiting dignitaries can use.
Smoking in all enclosed public spaces and places of work was banned under the Health Act 2006, and came into force in England in 2007.
It is not clear which Government department has amended the law for the venue or whether is only a temporary measure.