British MEPs have been lobbied to vote against the proposed free-trade agreement between the EU and US over fears of NHS privatisation.

As the UK's biggest trade unions prepare to debate motions that oppose the Transatlantic Trade and Investment Partnership (TTIP) at the Trade Union Congress in Liverpool on Wednesday 10 September, Len McCluskey, the general secretary of Britain's largest union Unite, has written to each UK MEP appealing for them to veto the treaty in the European Parliament.

Last week, IBTimes UK reported that Lord Livingston, the Trade Minister, would not be using a veto option to exempt public service from the wide-reaching agreement, fuelling fears that the UK will be left open to legal action from third-party companies should national health regulations impede on their profits.

Briefing journalists at Westminster, Livingston said: "The idea that this will lead to privatisation of the NHS is not true," adding that individual procurement groups will make decisions over whether to use US healthcare providers and that should TTIP come into effect, "the NHS will still look like it does today".

With the next round of negotiations scheduled to commence at the end of September, trade unions are set to increase their lobbying activity in an effort to increase public awareness of the agreement and to encourage a change of heart at the top table of government.

"There is a real and growing movement opposed to this dangerous deal. When people learn about TTIP they get angry and expect David Cameron to use his veto to protect the NHS. If the European Parliament is to have any legitimacy, MEPs must recognise that it is their job to reflect this anger, not the interests of Wall Street," McCluskey said.

"All MEPs have received a briefing which separates rhetoric from reality by revealing the full threat TTIP poses to the NHS. Contrary to the campaign of spin and disinformation coming from the European Commission and our own Tory government, TTIP could make the privatisation of health services irreversible," he added.

Pressure has mounted on the government to backtrack on its stance. The Labour Party has come out strongly in favour of NHS exemption. Shadow Health Secretary Andy Burnham said: "This will open the floodgates for private healthcare providers that have made dizzying levels of profits from healthcare in the United States, while lobbying furiously against any attempts by President Obama to provide free care for people living in poverty.

"With the help of the Conservative government, and soon the EU, these companies will soon be let loose, free to do the same in Britain."

In an interview with IBTimes UK earlier this year, Shadow Trade Minister Ian Murray, also of Labour, said: "That's certainly the position of the Social Democrat members of the European Parliament and Labour is part of that [referring to NHS exemption].

"They're very much of the view that the general utilities reservation [which would exempt public services] and ISDS [investor-state dispute settlement – the clause that protestors allege leaves governments vulnerable to legal action] are the red lines for them – and for us as well."

Livingston countered these statements, saying ISDS has been "misrepresented and misunderstood".

The UK is currently signed up to more than 90 ISDS clauses across all the free-trade agreements it has agreed in the past, with an aggregated running time of 2,000 years. Livingston said the UK has lost no cases pertaining to ISDS.