Major retailers in London stand to lose millions of pounds in lost trade due to the Tube strike.
Analysts say the strike could cost up to £50m to the London economy
Store representatives warned the industrial walkout would deter potential shoppers.
About five million people shop around Oxford Street, Bond Street and Regent Street daily, with 250,000 people passing through Oxford Circus station.
Some analysts have estimated the Tube strike could cost the London economy up to £50m a day.
"With the congestion on the buses people are just avoiding coming in to the centre of London," said Jace Tyrell, of the New West End Company, which represents stores in the Oxford Street area.
"If this continues it will be disastrous for the West End."
"Already looking out there it's much quieter than a normal midweek shopping day."
"The effect of the strike is compounded by its timing. This week is one of the most important shopping weeks for retailers as they launch new season ranges and prepare for the build up to Christmas."
But business groups warned the effects of the RMT's strike action could have a much bigger impact.
"A three-day strike will obviously cost sales on those days but they may be made up on other days," said Richard Dodd, from the British Retail Consortium.
"The longer the strike goes on, and the more often it happens, then the more likely it is that shoppers will give up shopping in London altogether."
Business group London First attacked the union for bringing the Tube network to a virtual halt.
Baroness Jo Valentine, the group's chief executive, said: "We don't need political shenanigans, we need everyone to work together to protect and improve the Tube."
"It is time for the RMT leadership to stop posturing and to contribute positively to the future of London's Underground services."
The strike by the RMT, which has closed two-thirds of the Tube network and affected 10 lines, is over pensions and jobs following the collapse of maintenance firm Metronet.