He told a meeting at the party's annual conference in Brighton on Monday that Labour had ‘saved the NHS since 1997'.
But he added that such gains would be at risk under the Conservatives, citing their plans to make GPs responsible for commissioning budgets.
‘It's all very well devolving everything, but you have to ask if [GPs] have the capability and skills to do that,' he said. ‘The risk is a lot of GPs will go to the wall. Andrew Lansley may not care about that, but we do.'
Mr O'Brien's comments came at a fringe debate on how the NHS would cope with the end of funding growth from 2011.
He stressed that the NHS was not facing £20bn of cuts, as has been widely reported, but had to find similar savings ‘much of which we want to reinvest in the health service'.
Solutions to the cash crisis aired at the event included a public list of poorly performing NHS managers, and a more outcomes-focussed QOF.
- Read the full version of this story in this week's GP dated 2 October.