A £448 million government initiative to fix problem neighbours has had "no significant impact", according to a leading think-tank.
The Troubled Families Programme, launched in the wake of riots in 2011, was designed to turn around the lives of 120,000 of the most "troubled" families in England by 2015.
It 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 - bringing the total cost to more than £1 billion.
But research by the National Institute of Economic and Social Research (NIESR) found no consistent evidence that the scheme - which sought to tackle often interlinked problems such as addiction, absence from school and anti-social behaviour - had improved the lives of those it aimed to help.
Using data from a quarter of the families that took part in the first stage of the programme, the NIESR calculated that there were "a very small number of positive or negative results", making the impact estimates "statistically insignificant".
"Across a wide range of outcomes, covering the key objectives of the Troubled Families Programme - employment, benefit receipt, school attendance, safeguarding and child welfare - we were unable to find consistent evidence that the programme had any significant or systematic impact," the report stated.
The findings come just two days after communities minister Lord Bourne praised the programme for "transforming the lives of thousands of families".
He wrote: "We know that more than 116,000 of the families who participated in the first phase of the programme have seen significant improvements in their lives, with children back in school for a year, reduced youth crime and anti-social behaviour, and adults holding down a job.
"We believe this programme has transformed the lives of thousands of families. The councils and frontline staff who have put it into practice should be pleased with the work they have done."
One author of the NIESR report, Jonathan Portes, told Channel 4's Dispatches programme: "The only way you can measure whether a programme has had actually any impact is to compare whether the people affected by the programme do better or worse than people who weren't affected by the programme, and we have that evidence.
"The Troubled Families Programme has no significant impact on any of the key outcomes it was designed to change.
"As far as we can tell, there's no evidence at all to suggest the programme had more than zero impact on any of the key findings it was designed to change."
Dame Louise Casey, who led the Troubled Families Team in the Communities and Local Government Department, is expected to answer questions from MPs on Wednesday.