Campaigners for the National Health Service are hoping that the House of Lords will delay the government's widely questioned Health and Social Care Bill.
Government sources say that an amendment tabled by crossbenchers could gain the support of the majority and result in the controversial bill being held up.
Lord Owen and Lord Hennessy have put forward the amendment, leading the health minister, Earl Howe, to write to peers saying that this could completely derail the NHS reforms.
Under the amendment, a special committee into the changes would report back by 19 December 2011, increasing the prospect that the legislation would not be completed by the deadline of April 2012.
In recent votes crossbenchers have voted against the government on a number of issues.
The health changes have been strongly criticised by professionals, doctors, patients and community groups.
In a recent open letter, more than 250 child health experts warned that the NHS reforms could prompt serious failings. They declare: "The inevitable fragmentation of NHS services will undermine our abilities to protect vulnerable children at risk from neglect and abuse, and compromise the safety and quality of care we provide for children with serious and life-threatening illnesses.
"Plurality and competition will disperse the already stretched service beyond being sustainable," the experts add.
Ekklesia associate Savitri Hensman commented: "It is clear that many parliamentarians – even within the Coalition – are worried about the Bill’s impact, but some will probably vote as the government tells them, whatever their own misgivings. Whether ministers can push the Bill through Parliament with only minor changes may depend on the level of public opposition."
* 'Health and Social Care Bill: privatising healthcare?', by Savi Hensman - http://www.ekklesia.co.uk/node/15533