The government will be forced to slash the number of academies it had hoped to create by September due to a lack of time and resources.
The Department for Education (DfE) had anticipated that the number of academies would triple by the beginning of the new academic year once the Academies Bill has become law.
But doubts have been cast on the Department's capacity to manage the conversion of so many schools in such a narrow time frame over the summer, particularly with a recruitment freeze in the civil service.
An impact assessment published alongside the bill estimates that a maximum of just 200 academies will be created this year and in each of the following three years, The TES can reveal. This would come at a cost of pound;33 million a year, the document says.
Education Secretary Michael Gove has pre-approved all schools rated outstanding by Ofsted for the change in status. Last week Mr Gove trumpeted the fact that more than 1,100 schools had expressed an interest in becoming an academy, of which 626 had been pre-approved.
But peers also cast doubts on Government ambitions this week following the bill's second reading in the Lords.
Liberal Democrat Baroness Walmsley, who speaks on education in the Lords, told The TES she felt the DfE had "over-egged" its aspirations on the number of academies opening in September.
"I don't think it will happen," she said. "It's very unlikely as there will be an enormous amount of work to be done. They have to consult all interested parties, they have to give teachers the time to process the offer. There are the serious legal sides to it, and the audits need to be carried out on the land and the buildings. I just don't think schools will have the time."
Fellow Lib Dem education spokeswoman Baroness Sharp said she felt schools had been given a "very misleading impression" by the offer of becoming an academy, adding that the DfE will have to revise its aspirations.
"I think it's quite obvious the Department doesn't have the capacity to process these schools," she said.
Shadow education secretary Ed Balls claimed that the policy had not been thought through. "The new government's academies programme is a total perversion of Labour's policy which was about turning round under- performing schools in disadvantaged areas.
"Michael Gove is removing the need to consult parents, local authorities and the local community and he will end up having to run hundreds and possibly thousands of schools from the centre.
"The new Government is now being forced to recognise this will not work."
But a DfE spokesman said: "We will ensure that all outstanding schools which apply can convert as soon as they have completed all the necessary legal steps and subject to the necessary legislation being passed by Parliament.
"But we have deliberately not set targets precisely so that schools go through this process at their own pace and don't feel pressured to convert by September."