Claims that a flagship intervention project had turned around the lives of 99% of England's most troubled families were misleading, according to a Commons committee.
The Government also overstated the financial benefits of the scheme when it claimed it had saved taxpayers £1.2 billion, MPs found.
They attacked the Department for Communities and Local Government (DCLG) for "unacceptable" delays and "obfuscation" in publishing an evaluation of the Troubled Families programme.
Some families have been pushed quickly through the scheme because the rewards for local authorities carrying out the programme are encouraging "perverse" behaviour, the Public Accounts Committee (PAC) also found.
MPs said the Government had failed to prove the effectiveness of the initiative, which was launched by David Cameron in the wake of the 2011 riots to turn around the lives of 120,000 families in England by 2015 and later extended to help an additional 400,000 families.
It follows the release of research in October by the National Institute of Economic and Social Research (NIESR), which had been commissioned to carry out an official national impact study, that found the scheme had ''no significant impact''.
Ministers had been accused of suppressing the critical findings after holding the information for more than a year before publication.
Meg Hillier, who chairs the PAC, said: "Government officials might be inclined to consider our comments on the delay in publishing its Troubled Families evaluation as a slap on the wrist about Whitehall bureaucracy.
"Let me assure them that given the ambitions for this programme, the implications for families and the significant sums of money invested, it is far more serious than that.
"But it is particularly important with a new initiative that there is transparency so that the Government can learn and adapt the programme."
The cost of delivering the programme was not taken into account when the government published a report in March 2015 claiming that it had saved taxpayers £1.2 billion, the PAC found.
It also said the success rate of the scheme was based on snapshots of how families were performing, which could include areas such as improved school attendance, rather than long-term results.
"The implication of 'turned around' was misleading, as the term was only indicative of achieving short-term outcomes under the programme rather than representing long-term, sustainable change in families' lives," the report said.
"While there was some success, by claiming that an outcome achieved meant that a family had been 'turned around', the department's use of the term overstated the impact of the Troubled Families programme."
Local authorities claimed reward payments for 116,654 families out of the maximum 117,910 for which they could claim in the first phase, the report said.
MPs called for the Government to review the payment-by-results system for the programme to stop councils trying to speed families through the system in order to receive funding.
Ms Hillier said: "The department has undermined any achievements the Government might legitimately claim for its overall work in this area.
"In particular, it was a mistake to use short-term criteria as the measure for successfully 'turning around' families, many of whom are grappling with long-term social problems.
"A tick in a box to meet a prime ministerial target is no substitute for a lasting solution to difficulties that may take years to properly address.
"We would also question the suitability of the Government's 'payment-by-results' model, which similarly risks incentivising quantity over quality.
"The department has now committed to providing Parliament with an annual report on progress with the Troubled Families programme, starting in March next year.
"For this to be meaningful, Government must be far clearer about the benefits that can be directly attributed to the public investment in it.
"Only then can Parliament and others properly assess the value for money of this programme and its merits as a model to bring about lasting change in the lives of those families it is intended to support."
DCLG said the evaluation was not suppressed, insisting data errors had caused significant delays in finalising the report.
A spokesman said: "As the PAC report recognises, the Troubled Families programme enabled local authorities to expand and transform the way local services work with families.
"But of course, there will always be lessons to learn and we have already made significant improvements to the second stage of the programme.
"We will look carefully at the evidence to find out how we can improve the programme further to help some of the most vulnerable people in our society."