The Public Accounts Committee says there has been a "systemic failing" in support to young people leaving foster care or children's homes.
Its chair Meg Hillier MP says young adults are "let down by the system that's supposed to support them".
The government says it is committed to improving the lives of care leavers.
The committee found outcomes for the 10,000 young people aged 16 or over who leave care each year are "poor and worsening".
Its report says the quality and cost of support to care leavers "varies unacceptably" between local authorities.
Ofsted has rated two-thirds of council care leaver services inadequate or requiring improvement, say the MPs.
"The scale of variability in the quality and cost of support, and a lack of understanding of what causes this, show that this is a systemic issue, rather than a problem in just a few local authorities," says the report.
Young people must leave local authority care by their 18th birthday "whereas 50% of all 22-year-olds still live at home" it notes.
These children have often had difficult lives with 62% in care because of abuse or neglect, it adds.
"Those leaving care may struggle to cope with the transition to adulthood and may experience social exclusion, unemployment, health problems, or end up in custody."
Some 41% of 19-year-old care leavers were not in education, employment or training in 2014 compared with 15% of the age group as a whole, says the report.
It welcomes government initiatives to improve the lives of care leavers and acknowledges more good practice is emerging but says there is more still to do.
"It's time the government reviewed its care leavers' strategy to make sure these young people get the full support they need," said Ms Hillier.
The Department for Education should take formal responsibility for improving the system, the MPs urge.
In particular they believe the DfE should improve care leavers' access to apprenticeships and training, suitable accommodation and better advice.
Town Hall bosses said 40% cuts to their budgets meant providing care leavers with adequate support was "becoming an increasing challenge" which councils could not handle alone.
"We urgently need to see the whole system properly funded and joined up to ensure children and young people receive the support they need, when they need it," said Roy Perry, chairman of the Local Government Association's Children and Young People's Board.
The Department for Education said its reforms would help care leavers make a successful transition to adulthood.
These include giving every care leaver a personal adviser and allowing young people to continue to live with their foster families after 18, though councils complain funding for the latter is "significantly underestimated".
A DfE spokesman said the government was also funding apprenticeship programmes for care leavers and encouraging Ofsted to focus more on care leaver support.
"But we want to go further, which is why we've committed to update the cross-government Care Leavers Strategy to improve support for these young people," said the spokesman.
Too many of the most vulnerable young people in England are "cut adrift when they need help the most", says the head of a powerful committee of MPs.