Councils have urged ministers to give them powers to check on academies to prevent standards from slipping.
Around 2,300 schools in England now have academy status, including half of secondaries, according to the latest figures from the Department for Education (DfE). Responsibility for their performance lies with the DfE.
But the Local Government Association (LGA) said they were concerned that as the number of academies grows, it will become more difficult for central government to monitor them - putting standards at risk.
They argue that councils should be put in charge of decisions on funding, improvement and intervention in areas where more than 50% of secondaries have become, or are becoming academies. There are 86 local authority areas where this is the case, the LGA said.
Without local oversight, under-performance in academy schools could be missed, and standards may slip, the association said.
Councillor David Simmonds, chair of the LGA's children and young people board, said: "Once the majority of secondary schools in an area have converted to academies, does the Secretary of State for Education have the capacity to monitor the performance of, and provide support to individual schools?
"We are concerned that by sheer weight of numbers, some academies may be left to fall through the cracks. We are particularly concerned about the majority of recently-converted academies that do not have a sponsor to keep an eye on their performance and step in with support if standards start to decline.
"Councils, with their local knowledge and democratic mandate, are better placed than civil servants in Whitehall to keep an eye on these schools and to spot the early signs of declining performance."
Academies are semi-independent state schools which receive their funding directly and have more control over areas including the curriculum and staff pay and conditions.
A DfE spokeswoman said: "Academies allow heads and teachers on the front line to make their own decisions - rather than local bureaucrats. They are raising standards and improving their results at twice the national average rate. But there can be no excuse for any school letting pupils down. We monitor performance in academies and, where they don't perform well enough, we will take action to make sure they do improve."
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