Struggling independent schools could seek academy status as a way of shoring up their finances, it is claimed.
The government wants to see a huge expansion in academies
The Independent Schools Council said it was expecting up to 20 fee-paying private schools to make the switch to take advantage of government funding.
Academies are privately run state schools, brought in by the government to raise standards in areas of educational disadvantage in England.
Ministers want to see at least 400, in the teeth of trade union opposition.
The head of research at the Independent Schools Council, Sam Freedman, said private schools might seek to become state-funded academies if they were struggling financially.
"Schools would only do it if they thought they weren't going to survive in the independent sector," he said.
"If I am a head teacher of an independent school, looking at my books, and I don't think I am going to survive past the next few years - one way I can assure my school will carry on is to become an academy.
"If I am not in financial trouble - there's no reason to become an academy because it's only going to mean giving up some independence."
He said he thought between 10 and 20 independent schools might seek academy status in the near future.
These were likely to be schools which faced a lot of competition locally from other independent schools or state schools with good results nearby.
So far four independent schools are known to have applied for academy status.
One, William Hulme's Grammar School in south Manchester, told the Times Educational Supplement the switch was a matter of survival.
"We could continue in the short-term, but in the long-term the situation was untenable," said head teacher Stephen Patriarca.
High performing independent day schools are already eligible to be considered for academy status if they can increase the supply of good school places serving diverse communities.
And former prime minister Tony Blair urged successful private schools to become academies or to set them up.
Until recently schools had to attract £2m from private sponsors to gain academy status, but the Children's Secretary Ed Balls announced plans to relax the rules on sponsorship for successful schools, colleges and universities.
Earlier this month, he told the Commons: "The test of whether an organisation can be a potential sponsor should not be its bank balance, but whether it can demonstrate leadership, innovation, and commitment to act in the public interest."
A Department for Children, Schools and Families spokesman said it would welcome any fresh proposals from good independent schools wanting to become academies.
"We want to increase the number of high quality non-selective free places in the state sector."
A spokesman from the Specialist Schools and Academies Trust which helps schools make the transition to academy status said: "We are always pleased to see more good state school places in the system and allowing independent schools to become academies is one way the government aims to achieve this."