Academies are the government's main vehicle for improving schools
Ministers have told England's largest sponsor of Academies it cannot take on any more schools until it improves standards at its existing ones.
The United Learning Trust, an Anglican charity, runs 17 of the new-style independent but state-funded schools.
Ministers say the group is doing "a good job in difficult circumstances" but are blocking new projects.
The trust says it expanded with the encouragement of the government, taking over very challenging schools.
Of the 13 Academies run by the trust which have been inspected recently by Ofsted, one was judged to be outstanding and three were said to be good. But seven were judged to be satisfactory and two unsatisfactory.
The trust's two Sheffield Academies were criticised by Ofsted this summer and judged to be inadequate.
The Sheffield Park Academy was put into "special measures" and the other, Sheffield Springs, was told to improve - a formal stage before special measures are imposed.
In terms of GCSEs, as a whole the trust's Academies have been improving at the same rate at other Academies.
The government says between 2008 and 2009, the improvement at the ULT Academies in terms of proportion of pupils getting five good GCSEs (A* to C) including maths and English was 5%, "in line with Academy performance overall".
And five out of 12 Academies which had been below the minimum level of 30% of pupils reaching this standard in 2007 had moved above it by this summer.
Schools Minister Vernon Coaker informed local councils about the government's decision in a letter.
Councils play a key role in finding sponsors for Academies.
The letter said: "It is quite clear that ULT has been bold and courageous in taking on some of the most challenging predecessor schools in the country.
"There are very high percentages of students with free school meals and special needs at ULT Academies.
"While there are encouraging signs, equally clearly, there is still some way to go before all ULT's Academies are making the consistent progress towards transformational change that is the goal and expectation of the Academies programme."
Mr Coaker added: "In view of the challenges it faces, and which it acknowledges, we have asked ULT to continue to focus in particular now on its existing Academies while developing two new potential projects".
The trust has said there has been "steady achievement" but that it welcomes the opportunity to consolidate and focus on its existing schools.
But it has also indicated that it expanded so fast because the government urged it to.
In a statement the trust said it took on Academies with the encouragement of the government, "often at the eleventh hour or when the Department has been unable to find another sponsor".
The statement says: "When ULT was formed in 2001 we expected to create one academy - Lambeth. The DCSF urged us to take on Ducie where no other sponsor was prepared to go and this became Manchester Academy which was awarded an Outstanding by Ofsted earlier this year.
"We thought in terms of 10 academies, but were encouraged to go beyond this until we now approach 20. It has been a remarkable path particularly considering the extremely difficult starting points of many of them.
"There has been a steady story of achievement reflecting our high standards and aspirations for each child and school by providing an environment in which teachers can really make a difference. Our performance at GCSE level including English and maths mirrors the achievements of the Academies Programme as a whole with an overall increase of 5.6% this summer."