The flagship troubled families programme will be a "challenge" for local authorities to deliver because the Government has ramped up the targets without proportionally increasing funding, a committee has warned.
Ministers set aside £448 million to help 120,000 high risk families when the scheme was originally launched but later announced another £200 million to extend it to a further 400,000 families.
In a report today, the Communities and Local Government Committee said the "additional workload is likely to challenge the capacity and resources of local areas".
Government must keep tabs on the expansion plans and "be prepared to provide more resources if necessary", MPs warned.
Under the troubled families programme households are assigned a dedicated worker to deal with a whole family on all of its problems, such as ensuring that the children attend school, appointments are met and appropriate services are accessed.
Committee chairman Clive Betts said: "The work of the troubled families programme is welcome. But it will be wasted if the families are abandoned when the programme ends in 2016.
"400,000 families were added to the programme in June, but the resources available have not increased proportionally. The Government needs to monitor this situation and must be prepared to provide more resources if necessary."
The warnings come as part of a wider report on the government's community budget reforms, which see services pool their funding to save cash and improve efficiency.
MPs found a "strong case that community budgets can deliver substantial savings is emerging" but the scheme is at risk of being the latest "shiny new idea" that is then replaced within a few years. They called on the Government to show strong leadership to ensure the scheme is introduced more widely.
Mr Betts said: "Community budgets are already demonstrating the clear potential to provide more effective public services, tailored to the needs of local people. As such, they offer a vital lifeline to local authorities grappling with increased demand for services and reductions to their budgets.
"Strong local leadership and a clear commitment from central government are now needed. Otherwise this potential won't be realised and community budgets run the risk of being consigned to the scrap heap of forgotten-about shiny new ideas.
"It is right to test a policy with pilots. But with yet another wave of pilots, we are reaching the point where progress may become bogged down in a plethora of pilots. The Government must send the clear message to every local authority, whether they are part of a pilot or not, that they will be supported if they wish to introduce community budgets."
Louise Casey, head of the Troubled Families programme, said: "The Troubled Families programme is making good progress with over 50,000 families being worked with and 14,000 already turned around, and we welcome the committee's support.
"This work is helping to reduce absences from school, youth crime and anti-social behaviour so will not be wasted at all.
"Families already turned around will continue to be supported as necessary and the new resources for 2015-16 and beyond will allow for more effective early intervention with families before their problems spiral out of control."