A "baffling" failure of Whitehall co-ordination means fewer than expected troubled families have been helped by Government schemes, a spending watchdog has said.
The Commons public accounts committee cited the "confusion and unnecessary duplication" caused by having parallel schemes run by separate departments as a factor in both being off course.
It called for further improvements in data-sharing, action to tackle wide reduce variations in the performance of the councils and firms delivering the help and an increase in the pace of progress.
In December, the National Audit Office said the "innovative and ambitious" programmes to help families with multiple challenges such as unemployment, antisocial behaviour and truancy were starting to have a positive effect but risked falling short of expectations.
A £448 million Department for Communities and Local Government (DCLG) "troubled families" scheme aims to "turn around" 120,000 families by May 2015 through incentives for local authorities.
At the same time, the Department for Work and Pensions (DWP) is seeking to place 22% of individuals attached to the programme into employment over three years to March 2015, with a budget of £200 million.
The NAO said the DWP programme had achieved only 720 employment outcomes, just 4% of its target, while none of the firms it was using to provide services had met the department's target.
By October 2013, the DCLG had achieved lasting improvements in the lives of 22,000 families, leaving a further 98,000 and was 13% behind.
The cross-party committee noted improvements - including the secondment of 150 Job Centre Plus advisers to local authorities - but said there remained too many barriers to coordinating the schemes and significant variations in performance between providers.
There was also an urgent need to calculate and publish the extent to which the programmes had saved the taxpayer money, it concluded.
Its chair, the Labour MP Margaret Hodge, said: "The two 'troubled families' programmes are designed to turn around the lives of some of the most disadvantaged families in our society, at the same time as delivering savings for the taxpayer.
"We welcome the commitment shown by both departments involved in delivering the programmes.
"However, we are concerned that the Government is on course to miss its targets of 'turning around' the lives of 120,000 troubled families and moving 22% of those referred to its employment programme into work by March 2015.
"Both departments have got to speed up the rate at which they are succeeding in their work."
She said the lower than expected performance "has partly resulted from the Government's baffling decision to implement two separate programmes for troubled families, which resulted in confusion and unnecessary duplication".
"Another challenge has been the departments' reliance on individual local authorities and private providers to deliver outcomes," she continued.
"There have been big variations in performance, which put achieving the programmes' objectives at risk.
"The departments must ensure that performance in each local authority, and by each contractor, is scrutinised to properly manage the contracts giving appropriate support where appropriate, but also imposing sanctions where necessary.
"We now need to see clear improvements in performance against targets and real cash savings made from these programmes.
"And the Government needs a clear plan for the delivery of the next phase of the Troubled Families programme, starting in 2015.
"These actions are essential not only to turn around the lives of the troubled families involved, but also to deliver savings and demonstrate value for money."
A Government spokesman said the Troubled Families programme was "on track" with more than 22,000 families turned around in 18 months.
"This means children are back in school, youth crime and anti-social behaviour is significantly reduced, and adults are either in work or on a path to employment. But there is always more to do and we expect performance to improve even more over the next year," the spokesman said.
"Over 100,000 families have now been identified for help through this programme and over 78,000 are being actively worked with. Together, these programmes provide value for money for the taxpayer through payment by results, which is better for taxpayers and those we are supporting on the programme."