A Brexit would protect the NHS from interference by the "dysfunctional European Union", a former Labour foreign secretary will warn.
Lord Owen will say that successive governments have accepted an EU market in health, which has become "entrenched" in the NHS.
The peer, who campaigned as health minister to remain in the European Economic Community in the 1975 referendum, will launch Vote Leave's 'Save our NHS' campaign in London on Wednesday.
He is expected to say that a vote to leave the EU would allow the UK to take back control of the NHS and protect it from outside competition.
He will say: "The EU/Eurozone from 1992, in marked contrast to the old European Community of 1975, creeps into every nook and cranny of our life.
"It is now becoming entrenched in the NHS and this June we have a once-in-a-lifetime opportunity to get it out."
He will continue: "Now is the time to take back control from the EU and protect our NHS for future generations.
"We are agreed in Vote Leave, that whatever our political views on the present marketisation of the NHS, decisions on the NHS should for the future be for the UK Parliament and devolved administrations to take.
"It should not be for the European Commission nor the European Parliament."
He will argue that the NHS would be freed from any competition-and-market-led involvement from the European Commission, including a proposed transatlantic free trade deal between the EU and the US.
Critics fear the Transatlantic Trade and Investment Partnership (TTIP) between the EU and the US would lead to American health providers targeting the NHS.
'If people Vote to Leave on 23 June - as I hope they will - it will automatically follow that no British government can ratify the present TTIP.
"Thereafter, UK legislation will govern the NHS in future and as a consequence we can take back control and protect the NHS from the EU."
The Government has insisted the TTIP does not threaten the UK's health service, but offers trade openings for British business.