An official evaluation, due to be published in July, is expected to find little or no evidence that the ambitious project's early targets have been met in England.
In Wales, there are 450 Sure Start projects spread across every local education authority and plans for each to have an integrated under-fours centre. The cash comes from the Assembly government's children and youth support fund, Cymorth, and the scheme is being evaluated this summer.
Labour has promoted Sure Start as one of its major success stories and pledged a huge expansion of the scheme if re-elected. Around pound;1 billion has so far been spent, and up to pound;1.8bn per year pledged to help build a nationwide network of 3,500 new children's centres.
But Norman Glass, chief executive of the National Centre for Social Research, said that while anecdotal evidence suggested both parents and staff were enthusiastic about Sure Start, the evidence so far did not support them.
An early evaluation report from Birkbeck college, London, said levels of special needs had actually risen among children starting school in Sure Start areas - probably because of unmet need being identified.
And the scheme has yet to hit initital targets on reducing speech and language problems, smoking during pregnancy, children returning to the child protection register and children in workless households.