An academy sponsor has entered talks with the Government about its plans to open a "super-chain" of up to 250 state schools within five years.
E-ACT, which runs 11 academies, is developing rapid expansion plans that would make it by far the biggest schools' group in the country, dwarfing the vast majority of local authorities.
It aims to run dozens of academies, free schools and primary schools as power is shifted away from councils. Currently, the biggest academy sponsor is the United Learning Trust, which runs 20 schools and a city technology college.
Ministers have repeatedly given their support to collaboration between schools, citing greater improvements in exam results for academies in chains and federations. However, no chain has ever laid out such ambitious plans for growth.
Sir Bruce Liddington, E-ACT's director general and a former schools commissioner at the Department for Education, said he had spoken to ministers and civil servants about rapidly expanding the number of schools the charity runs. He aims to double the number of its schools in the next three years and "significantly" expand to as many as 250 in five years.
Sir Bruce told The TES that he expects the group to have around 50 free schools, 50 "traditional" academies that replace underperforming schools, 100 "converter" academies and 50 primary schools.
"Our plans show a continuation of our core purpose to replace underachieving schools in disadvantaged parts of the country," Sir Bruce said. "It is then to move into academy converters with schools that are by no means failing, but are not outstanding and are directed by the department to have a partner such as ourselves."
Sir Bruce said that E-ACT was "really very keen" on free schools, which would allow the chain to respond to what parents want. "I'm hugely excited about the opportunity for flexibility and we intend to take advantage of that," he said.
"We are also interested in chains of primaries. As funding becomes tighter you will find that small primary schools will need to get together if they are going to survive. We are also starting to talk about chains of primaries in inner-urban areas around our existing traditional academies."
Mary Bousted, general secretary of education union the ATL, criticised the expansion of school chains. "Here we see the reality of free schools and academies," she said. "Despite Michael Gove's protestations about setting schools free and having local autonomy, this will result in tax payers' money going to unaccountable and unelected mandarins."
Russell Hobby, general secretary of heads' union the NAHT, said large chains could become bureaucratic "private local authorities" that would be difficult to hold to account. He also said there were ways for primaries to remain "sustainable" without entering into chains.
"I have nothing against chains per se, but I do have concerns about big empires," he said. "One of the risks is the predatory chain gobbling up schools, saying `come with us or else you'll be stranded'. I'm not saying that's the case with E-ACT, but it is a risk of the system."
A DfE spokesman said it had not discussed specific numbers of schools with E-ACT, but reiterated the Government's support for chains.
"Academy chains and federations have had huge success to date in driving up standards in the lowest performing schools - much faster than standalone academies or the average maintained school."
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E-ACT has claimed success in the academies it already runs, with about 10 per cent more pupils achieving five good GCSEs with English and maths, according to Sir Bruce Liddington, its director general.
But it has also attracted controversy, with plans for one academy having to be dropped after the charity faced allegations of financial mismanagement in 2009. Sir Bruce has also been criticised for his salary package of up to pound;265,000 a year and for claiming expenses for a stay in a luxury hotel - money which he has since repaid.