The group, called No Health In TTIP East Midlands Alliance, raised the boards to to demand action from Kettering MP Philip Hollobone over a trade deal which they say threatens the future of the NHS.
The campaigners have repeatedly called upon the Eurosceptic MP to support their call to exclude the NHS from an EU trade deal.
The campaign group says the refusal by the Tories to exempt the NHS from the American trade deal flies in the face of legal advice seen by health campaigners which it says confirms there are clear dangers arising from the Transatlantic Trade and Investment Partnership that could impact on the NHS.
The TTIP trade deal is being negotiated behind closed doors, between EU and United States delegates.
It is the largest bilateral trade deal ever negotiated and campaigners say it threatens to make the ongoing privatisation of the NHS irreversible.
Campaigners fear TTIP could grant American multinationals, or any firm with American investors, the power to sue the government if it ever attempted to take privatised health services back into public ownership.
Local spokesman Ron Duvale, of The Oval, Kettering, said: “Our local MP must get to grips with the threat TTIP deal poses to the NHS.
“Philip Hollobone should ask to see the legal advice being withheld by the Government about the NHS and TTIP.
“Hundreds of households are sending a clear message that people across Kettering do not believe it is right for our NHS to be put at risk of irreversible privatisation.
“If Philip is serious about his concerns about the EU then he should demand that David Cameron acts and protects the NHS from the EU trade deal called TTIP.”
Mr Hollobone has previously addressed the group’s concerns by saying: “Local residents don’t need to hold a demonstration to let me know their views.
“I am readily contactable by telephone, post, email or in person and am in contact with hundreds of residents each and every week about matters of concern local and national.
“The proposed TTIP trade deal between the EU and the USA poses no threat to our NHS, as has already been stated in the House of Commons on many occasions.
“on June 10 last year David Cameron said in reply to a question from Harriet Harman MP: ‘On the question of TTIP, I would argue that the NHS is protected. There is no way that a TTIP agreement can lead to changes in our NHS. I suggest to the Labour Party that instead of raising the profile of a threat that does not exist and trying to seek false reassurances, it would be better if the whole of the UK political system could come together and push the Americans to go further and put more on the table, so that this trade deal benefits working people in Britain.’
“But if this campaign group don’t believe either me or the Prime Minister they can join me in voting to leave the EU when the referendum is held so that the trade deal won’t apply at all.
“In the meantime, the Conservative Government is pumping a record £10bn more of taxpayers’ money into our NHS over the next five years.”