Services aimed at helping jobless teenagers could suffer if councils face further funding cuts without substantial reform, local authorities have warned.
A Local Government Association (LGA) survey of town halls found just 7% of councils said they had the powers and funding needed to meet their legal duties to address the number of teenagers not in employment, education or training (Neets).
Nine out of 10 local authorities have been forced to reduce spending on support for 16 to 18-year-olds, the LGA survey of 87 authorities revealed.
David Simmonds, chairman of the LGA's Children and Young People Board, said: "Councils are determined that every young person realises their full potential.
"Despite challenges, we are proud of our leading role working with different governments to consistently increase youth engagement over the last 15 years.
"The message from local government is clear. Cuts without reform risk undoing all of our collective good work, putting thousands of promising futures at risk.
"Councils are uniquely well placed to help young people access the opportunities created by the local employers increasingly frustrated by remote national institutions. It is important that we have the powers, levers and funding to fulfil our legal duties to young people.
"The new Government has a real opportunity to build on recent successes and meet its ambition of full employment by enabling local partnerships of councils, schools, colleges, jobcentres and employers to locally coordinate a single youth offer. It will ensure every young person is either in work or learning.
"Over decades, services supporting young people's journey from school to the world of work have grown more complex and disjointed. With the greatest will, this cannot be resolved by national government alone.
"Councils and local partners know that, with the support of government, they can join-up advice, skills and experience around the needs of each young person and local employers to help more reach their potential and ensure no vulnerable youngsters get left behind."
The survey found that 91% of councils claimed their capacity to deliver their statutory duties to support the participation of 16 to 18-year-olds had been reduced as a result of government reductions to their budgets.
The LGA called for Whitehall to return key powers over careers advice and skills to councils.