A flagship Government employment scheme has been branded ineffective by half the organisations paid to deliver it, according to a leaked report.
Documents seen by Channel 4 news also suggest that Work Programme clients with health conditions and disabilities are "being seen less often and being offered less support than other groups".
Research by independent experts, Work Programme Evaluation : Interim meta-report, was ready to be published six months ago but ministers blocked its release, according to the programme.
It is reported to have found a quarter of providers thought it "very ineffective" while 22% believed it was "somewhat ineffective" and 10% thought it was "neither effective nor ineffective".
Under the Work Programme, providers from the voluntary, private and public sectors are paid according to results to get people into work, with extra incentives to support the hardest to help.
But, a ccording to Channel 4 News, the report states that there is "no clear relationship between an individual participant's Work Programme payment group and the nature and intensity of support that participant received, which suggested ... that the differential payment regime was unlikely to have effectively mitigated creaming and parking."
The Work Programme has come under attack since its launch in June 2011 and statistics last June showed that just 5% of the hardest to help people had been found work.
Margaret Hodge, who chairs the powerful Public Accounts Committee, told Channel 4 News: "Officials assured us that the design of the programme was such that there was no way the private providers could ignore their (clients) needs.
"What the leaked report has shown us now is actually those needs have been ignored and those that need most help are not being given it."
She added: "One of the problems we find consistently at the Department for Work and Pensions is they are not transparent, they are not open.
"We have been trying and trying to get the performance of providers as transparent data that we can analyse. They always refuse to do it and surprise, surprise, the day before we have a hearing you always find the trade association representing the providers, they put forward data which of course has not been verified either by the Office for National Statistics of the National Audit Office."
Mrs Hodge said she was " worried about payment by results".
She added: "I'm worried they have got it wrong. I think it's ideology, it's not pragmatic and I'm absolutely convinced that when we look at the Work Programme again we will see that there are things that are wrong in the design of the programme and payment by results is not delivering.
"We are wasting hundreds of millions of pounds on it."
A Department for Work and Pensions spokesman said:? ?"The reality is that the Work Programme is working. Around half a million long-term unemployed claimants have started a job through the Work Programme - a scheme designed to radically change how we support the hardest to help jobseekers while giving taxpayers a good deal by only paying for results.?
?"Previous schemes simply didn't do enough for disabled people or the long-term unemployed. Since we launched the scheme in 2011, we have taken action to drive performance up significantly and we are committed to making sure providers continue to improve the service they give to jobseekers. Any draft interim analysis from the early days of the programme won't take these improvements into account."?