Downing Street was forced to back down last night after a rebellion by some of David Cameron's own MPs threatened an embarrassing defeat in the Commons.

Up to 30 Eurosceptic Tory MPs vowed to join their Labour and SNP counterparts in supporting an amendment to the Queen's Speech which explicitly protects the NHS from the Transatlantic Trade and Investment Partnership (TTIP).

Labour leader Jeremy Corbyn said his party would join forces with the Conservative MPs, opening up the prospect that the government could be defeated on a Queen's Speech for the first time in almost 100 years.

Eurosceptic Tory MPs, led by the former cabinet minister Peter Lilly, wanted to ensure that the NHS is protected from US multinationals in trade arrangements struck as part of TTIP. A vocal critic of TTIP, Corbyn has nevertheless maintained that "staying in the EU was the best way to fight its provisions", says Sky News

Opponents of the deal claim the highly controversial EU-US trade deal will force the health service to allow private US pharmaceutical firms to bid for lucrative contracts, paving the way to privatisation through the back door.

Officials in Brussels and Westminster have countered that the deal will contain a similar provision as that in the finalised, but not yet in force, Comprehensive Economic and Trade Agreement (CETA) with Canada. This "states that 'public utilities' — including health services — can be provided by a state monopoly or can be limited to a certain number of private providers", notes Full Fact.

The wording is designed to prevent nationalised services from being forced to open up to private competition, but obviously it has yet to be tested legally.

An unusual alliance

The issue has been seized on by Brexit campaigners "who struck an unusual alliance with Jeremy Corbyn's Labour", says the Daily Mirror.

The move by pro-Brexit Tories is an attempt "to highlight their claim that the NHS is being undermined by Britain's EU membership – an argument that it believes will sway voters", says the Financial Times.

It will, however, "infuriate Downing Street, who attempted to use the unveiling of the Queen's Speech to set a fresh agenda for the party after the 23 June poll", says The Independent.

"As we've said all along, there is no threat to the NHS from TTIP. So if this amendment is selected, we'll accept it," a Downing Street spokesman said.

As details of the rebellion emerged yesterday, a ministerial ally of the PM described the move as "opportunistic". But, in what the Mirror said represents a "major climb down", Downing Street yesterday said it would accept the rebel amendment.

The BBC's assistant political editor Norman Smith said that while accepting the amendment is an embarrassment for Cameron, a first defeat over a Queen's Speech since 1924 would have been a greater humiliation.