Most voters in key battleground constituencies want David Cameron to protect the NHS from a new trade deal which campaigners claim threatens privatisation of health services, a new survey has found.
More than two-thirds opposed the inclusion of the NHS in negotiations over the Transatlatic Trade and Investment Partnership (TTIP), a poll of more than 2,600 adults in 13 marginal Conservative constituencies for the Unite union showed.
Critics warn that the trade deal is being negotiated behind closed doors of the European Commission between EU bureaucrats and delegates from the United States.
Unite general secretary Len McCluskey said: "The Tories' Health Act of 2012 opened our NHS up to profit-making US private firms and a new trade deal threatens to make the sell-off permanent. It's clear from this poll that the NHS is going to be a major issue at next year's election.
"The results prove that people firmly oppose the inclusion of the NHS as part of the trade deal. A majority of people even think that David Cameron should use Britain's veto.
"David Cameron's silence is deafening. He is refusing to answer a very simple question: Are we going to exempt health from the EU US trade agreement?
"Unless he acts, the NHS will be at the mercy of US companies and Wall Street investors who will be able to sue the Government in secret courts if it tries to reverse privatisation."
Damian Lyons Lowe, chief executive of Survation which conducted the survey, said: "When the potential implications of this trade deal are put to voters, they are clear that protecting the NHS is of paramount importance, notwithstanding the benefits of a trading partnership.
"As this poll shows, healthcare is an issue that cuts across political divides and so may prove critical to MPs in marginal constituencies sitting on very small majorities. Should public awareness become widespread, this could, based on our polling, become an electoral liability for David Cameron if he does not heed public concerns."
The constituencies where the polling was held were Amber Valley, North Warwickshire, Broxtowe, Lancaster & Fleetwood, Brighton Kemptown, Lincoln, Morecambe & Lunesdale, Sherwood, Thurrock, Cannock Chase, West Dorset, Camborne & Redruth, and Truro & Falmouth.
The government denied that any deal would lead to the privatisation of the NHS and insisted it would create jobs.
A Department of Health spokesman said: "We have no intention of allowing the TTIP to dictate the opening up of NHS services to further competition; and it will not do so. The NHS will always be free at the point of use for everyone who needs it."
Syed Kamall, leader of the Conservatives in the European Parliament, poured scorn on the "myths' surrounding the TTIP negotiations.
Blogging on the Huffington Post UK, he wrote: "If the TTIP negotiations cover issues other than trade, it becomes known as a "mixed agreement" and will have to be ratified by the British Parliament.
"Democratic oversight and transparency is a core shared objective of the parties and Members of the European Parliament across the political spectrum are closely monitoring the different stages of the process in order to inform our citizens and to engage them in the process."