Plans to suspend London's congestion charge between Christmas and New Year, have been announced by the mayor.
Critics say the congestion charge has reduced sales in central London
A consultation exercise has begun on whether the £5-a-day charge should be put on hold for the three working days.
Ken Livingstone says it would benefit shoppers, businesses and residents at the start of the sales.
Meanwhile a report by the Liberal Democrats says drivers of 4x4 vehicles should pay double to enter the zone to cut pedestrian injuries and pollution.
Research by the party showed the number of 4x4s in London, as a proportion of the total number of cars bought, was higher than anywhere else in the UK.
Lib Dem spokesman Lynne Featherstone, said: "Four-by-four vehicles in city centres are a danger to pedestrians, a potential hazard to other road users, can cause more damage than any other type of car and takes up more road space, so increasing congestion.
"The congestion charge has been a success, but the series of proposals we have put together for the zone are to make it easier and more effective."
The Lib Dems said the original charge was "outdated and flawed" and their study also called for the toll to end at 1700 BST rather than 1830 BST and be scrapped at Christmas and New Year.
But Mr Livingstone said his announcement of plans to suspend the charge for three days was part of his manifesto commitment.
The mayor, who has previously called 4x4 drivers "idiots", also said he would look into whether it would be possible to charge them double.
Critics of the charge have said it is damaging central London businesses such as John Lewis, which said sales were down 9% at its Oxford Street store.