Ministers have been accused of suppressing a critical evaluation of the Government's Troubled Families initiative which cast doubt on the effectiveness of the programme.
The initiative, launched in the wake of riots in 2011, aims to turn around the lives of thousands of families by tackling often interlinked problems like addiction, absence from school and anti-social behaviour.
But BBC Newsnight has seen an unfavourable and unpublished report apparently held by the Government since last autumn which suggested the programme had no discernible impact on things like unemployment and criminality.
A senior civil servant told Newsnight the report was "damning" and attacked the scheme as "window-dressing".
The Troubled Families programme, costing about £400 million, was launched in 2012 with the aim of turning around the fortunes of 120,000 households by 2015.
The initiative was then extended for a further five years starting in 2015/16 to help an additional 400,000 families with hundreds of millions of pounds earmarked for the task.
Ministers committed to measuring whether or not the policy worked, with a consultancy called Ecorys leading the work.
But that analysis, seen by Newsnight, has apparently never been published.
An official who had read the report told the BBC it was being suppressed because of its findings.
The official analysis of data from dozens of local authorities found that "the lack of obvious effect from the programme across a range of outcomes indicates that the programme did not have a measurable impact on families within the time-frame over which it was possible to observe its effects".
It also found there was "no discernible impact on the percentage of adults claiming out-of-work benefits either 12 or 18 months after starting on the programme" and "no obvious impact on the likelihood that adults were employed 12 or 18 months after starting on the programme".
Meanwhile, participation in the programme "did not have any discernible impact on adult offending" seven to 18 months after the family joined the initiative.
The researchers did report some problems with data quality and representativeness.