The government has been defeated at the Labour conference over its NHS plans.
NHS Logistics staff are striking over the sell-off of the supply agency
Delegates voted in favour of a Unison motion calling for a slow down in the pace of reform and condemning the privatisation of the health service.
It comes on the day health workers at NHS Logistics are on strike over plans to sell-off the supply agency to DHL.
A NEC statement supporting reforms was also defeated on the back of the union "block vote" but Labour said 62% of ordinary members had supported it.
Labour sources said that 87% of trade unions and other groups affiliated to the party opposed the statement backing the health reforms but promising greater consultation.
A party spokesman said the card vote had showed a majority of constituency supported "Labour's commitment to continue the reforms in the health service which are bringing benefit to patients across the country".
Ahead of the Unison vote, the union's general secretary Dave Prentis had told the Manchester audience ministers must sort out the "mess" .
Any organisation which refuses to make difficult decisions to get back on track is an organisation which in a few years will have to make even more difficult decisions
Proposing the motion attacking the "breakneck speed of reform", Mr Prentis said: "Leave the privatisation and failing markets to the Tories.
"Set that clear red line between us and the Tories. This is their agenda not ours.
"If you believe the NHS is that jewel. We need to protect it."
In his speech, he attacked plans to privatise NHS Logistics and also the policy of reconfigurations which could lead to major hospitals being stripped of key services such as A&E to provide more care in the community.
But he was cut short before completing his motion - as he had exceeded the five-minute limit - to heckles from the conference hall, which included NHS staff waving placards saying "Save Our NHS" and "Keep the NHS Working".
The motion called on the government to "rethink the headlong rush to a competitive system".
It warned: "Immense damage is being done to some local services because of deficits and the breakneck speed of change".
The Unison motion, which does not change government policy, was support by a number of speakers.
David Williams, a delegate from Selly Oak, said: "I didn't join this party to see this privatisation programme. I joined this party to defend the health service.
"What we are seeing here is a process of losing support and losing votes among the very people that we look to for support in election after election."
And Sharon Holder, of the GMB union, said NHS staff were "alienated" by health reforms.
"They are fed up with competition, fed up with PFI, fed up with privatisation."
Unison proposed the motion opposing NHS reforms
But a few speakers supported the government's record on the NHS, praising the investment.
Kent GP Dr Rav Seeruthun warned delegates not to let their objections get in the way of patient care and accept private sector involvement was sometimes necessary.
And Betty Carey, a Labour member from Wansbeck, in Northumberland, added Labour had helped improve many aspects of the NHS and social care because of their huge amounts of investment.
Health Secretary Patricia Hewitt, who had urged Unison to drop the motion, saying the government, trade unions and NHS staff should work in partnership, said the health service was facing a "challenging" period.
She added change was inevitable. "Any organisation which refuses to make difficult decisions to get back on track is an organisation which in a few years will have to make even more difficult decisions."
But delegates ignored her pleas and voted in favour of the Unison motion.
Shadow health secretary Andrew Lansley said: "This vote exposes further divisions within Labour about its future direction."
And Liberal Democrat health spokesman Steve Webb added: "The government is pressing ahead dogmatically without stopping to see whether its reforms are actually improving patient care."
The public sector union tabled the motion as hundreds of staff from NHS Logistics were manning picket lines at five supply depots in England.
The agency, which delivers everything from bedpans to medical equipment and food to GPs and hospitals, is due to be transferred to delivery firm DHL at the beginning of October.
It is their second 24-hour strike in a week and ends on Wednesday night.