Protests will be held in towns and cities across the country today against a major trade deal that campaign groups believe would hit jobs and public services.
Opponents claimed that a proposed deal between the European Union and the United States, known as the Transatlantic Trade and Investment Partnership (TTIP), is the result of "secret" negotiations between US officials and the European Commission.
Hundreds of people are expected to join protests in London, Edinburgh, Brighton, Manchester, Cardiff, Nottingham and other areas.
Groups opposed to the deal say it threatens increased privatisation of schools and the NHS, would cut food and environmental rules, and cost jobs.
Nick Dearden, director of the World Development Movement, said: "The deal would hand multinational companies unprecedented powers over life in this country."
Unite general secretary Len McCluskey said: "David Cameron has shown that he's willing to go to Europe to defend bankers' bonuses. Now he must use his powers to defend our cherished NHS.
"The most significant effect will be felt in health, enabling US healthcare multinationals and Wall Street investors to sue the UK government in secret courts if it attempts to reverse privatisation."
Business Secretary Vince Cable has said: "There is no question of TTIP being used to promote an ideological agenda for the NHS. There is no suggestion whatever that the TTIP negotiations could be used to undermine the fundamental principles of the NHS or advancing privatisation.
"The NHS will always be there for everyone who needs it, funded from general taxation, free at the point of use."
Green Party leader Natalie Bennett said: "The proposed deal threatens to blow apart the power of our democratic decision-making. TTIP is a huge threat to hard-fought-for standards for the quality and safety of our food, the sources of our energy, workers' rights, and our privacy.
"The harmonisation of food standards is particularly concerning. Under the deal, food products include chemically-washed poultry, livestock treated with growth hormones, and genetically modified crops - all allowed in the US - could be sold in the UK."
Green MEP Jean Lambert said: " TTIP supporters push the myth that more trade means more jobs. It doesn't.
"There is no guarantee that TTIP will be good for job creation - let alone decent jobs that pay enough to live on, respect labour rights and promote high health and safety standards."