Direct action group UK Uncut said that thousands of people, including health workers, trade unionists, pensioners and comedians like Josie Long and Mark Thomas, will be among those occupying Westminster Bridge.
The protest, described as a "spectacular act of mass civil disobedience", is being held just days before the House of Lords debates the Health and Social Care Bill.
Organisers described the demonstration as a “last-ditch attempt” to defeat Health and Social Care Bill 2011, which passed in the Commons on September 7.
The bill aims to make the biggest changes to the NHS in its history and includes a part that states the secretary of state will no longer have a duty to provide health service to all citizens. Opponents see this as a Conservative-led coalition government attempt to move towards a controversial US-type system where the money-grabbing private sector can take over lucrative parts of healthcare.
The bill goes to the House of Lords on October 11 where it will face stiff resistance, including from prominent members of the ruling Liberal Democrats.
A spokesman for UK Uncut said, of Sunday’s bridge blocking protest: “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.”
The demonstration will begin at 1pm on Sunday. Organisers say the purpose of blocking the bridge is to symbolically kill the movement of the bill, whose effects would travel from Parliament, on one side of Westminster Bridge, to St. Thomas’ Hospital - one of Britain’s oldest medical institutions - on the other.
The campaign has won huge grassroots support.
In response to criticism, legal spokesman for the Department of Health said: “the removal of the duty to provide (proposed by the bill) does not in any way undermine the secretary of state's accountability or responsibility for the health service.”
"We accepted all of their recommendations to strengthen the Bill but the most destabilising factor for the NHS would be greater uncertainty and delay of reform to the ultimate detriment of patients.
"We simply won't secure the future of the NHS without this Bill."A UK Uncut supporter told The-Latest: “I'll be on the bridge so that when my kids ask me what happened to the NHS, I can at least say 'I tried'.”
UK Uncut uses direct action to get its message across, often closing down high street stores that are owned by tax avoiders.
Vodafone was targeted after Private Eye exposed a deal they made with HM Revenue and Customs, which substantially reduced the amount of back taxes that they had to pay. Vodafone were originally found liable for £6 billion, but negotiated the amount to be paid down to under £2 billion.
Sir Philip Green and the Arcadia Group's shops including Topshop, BHS, and Burton have been targeted as the group is owned by Phillip Green's wife, who lives in Monaco where she does not have to pay income tax.
Boots was targeted on January 30 2011. Three people needed hospital treatment after police used CS spray on protesters.
Fortnum & Mason and their parent company, Wittington Investments were targeted during the March 26 2011 anti-cuts protests for their tax avoidance policies. This took the form of a peaceful mass sit-in. The police arrested and charged 138 protesters with "aggravated trespass".
A video obtained by The Guardian backed up protesters' claims that senior police officers tricked them, arresting them after assurances that they were being led to safety. As of July 5 this year, legal action against five minors were dropped, 13 were expected to enter plea bargains at City of Westminster magistrates and charges remain against 139 others.
Protests against the greedy bankers who sparked the world economic crisis have been taking place in America, particularly New York. The Occupy Wall Street movement has brought thousands of demonstrators to the streets and police have mounted mass arrests.
* Here's information about how to get involved in the London demo.