Direct action group UK Uncut has called on its supporters to occupy Westminster Bridge as a protest against the Government's health service reforms.
UK Uncut says that it is planning "a spectacular act of mass civil disobedience" and will bring traffic to a halt on Sunday 9 October.
Westminster Bridge, flanked on one side by the Houses of Parliament and on the other by St Thomas' Hospital, has potent symbolism.
UK Uncut claims that "by blocking Westminster Bridge, we symbolically block the bill from getting from Parliament to our hospitals".
The protest will start at 1pm and the group encourages participants to adopt shock tactics such as lying in pools of fake blood and performing mock operations.
A UK Uncut spokesperson said: "Yes, it will be disruptive. Yes, it will stop the traffic. But this is an emergency and if we want to save our NHS we need to shout as loud as we can."
UK Uncut says it will maintain close contact with St Thomas' Hospital to ensure access for emergency vehicles.
• Westminster Bridge was closed to traffic last Sunday for the Tour of Britain cycle ride. The closure caused severe traffic congestion in the Waterloo area.