A £448 million Government initiative to fix problem neighbours has had "no significant impact", according to analysis by a leading think tank.
The Troubled Families Programme, launched in 2012, was designed to turn around the lives of 120,000 of the most "troubled" families in England.
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 programme, the NIESR calculated that there were "a very small number of positive or negative results", making the impact estimates "statistically insignificant".
The findings come just two days after the 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."
Lord Bourne continued: "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."