MPs passed the Care Bill on Tuesday night, including the hospital closure Clause 119, giving Health Secretary Hunt power to begin a mass closure of hospitals.
He can close hospitals on just 40 days notice.
A total of 297 MPs voted in favour of Clause 119, while 239 voted against, including six Tories and one LibDem.
Labour lost an earlier vote to remove the clause entirely from the bill, while LibDem MP Paul Burstow withdrew his support for his own amendment to the clause at the last minute.
The clause was inserted into the Care Bill after the High Court ruled last October that Hunt had acted outside his powers when he decided the emergency and maternity units at Lewisham Hospital in south-east London, should be cut back, when neighbouring trust Queen Elizabeth Hospital was found to be in debt.
Hunt will now be able to appoint Trust Special Administrators (TSA) who will take over ‘failing’ NHS trusts in England and be able to legally push through whatever local closures they want.
The TSAs will have the power to close or downgrade any hospital within 40 days.
Rachael Maskell, head of health for Unite said: ‘Today is another dark day for our NHS under this government. It has seized extraordinary powers to close hospitals, forbidding communities to mount any defence of the services they rely upon.
‘Conservative and Liberal Democrat MPs should be thoroughly ashamed of their conduct. They colluded to take away our voice. But come the next election we will make sure it is they who lose not just their voice but their seats.
‘Every time that clause 119 is abused, Unite will ensure that the voices of the people and their health professionals are heard, and that voters understand exactly who betrayed the NHS.’
Ohan Azam, GMB National officer, said: ‘This vote means the government can asset strip a hospital in 40 days.
‘The reason we were campaigning against clause 119 is that we think that decisions on hospitals should be taken by local people and clinicians.
‘The danger is that hospitals that are doing really well will find themselves in the firing line.
‘297 MPs let down the public very badly and they will be held to account for this.
‘We need a national campaign of action that engages local people to make sure our hospitals are protected.’
BMA member Anna Athow told News Line: ‘With this vote they have thrown down the gauntlet. The trade union movement must pick it up. Just verbal opposition is hopeless!
‘The Tories intend a massacre of A&Es and NHS hospitals. The trade unions must stop hiding. Hospitals must be occupied to stop closures and a general strike called to defend the NHS by bringing in a workers government.’