Ministers are making struggling schools become academies even when the costs are disproportionate to the benefits, a leaked government document suggests.
Civil servants planning for budget cuts at the education department suggested ministers consider value for money before forcing academy conversions.
But Education Secretary Michael Gove overruled this cash-saving idea as "totally wrong", the document reveals.
The education department says academies are the best way of improving schools.
But the National Union of Teachers said Mr Gove's "pet policies are driving the education agenda at any cost".
Academies are privately run schools funded by the state in England. They have control over their own admissions, and increased freedoms over what they teach and pay staff. They can get up to £110,000 in start-up costs.
Where underperforming schools are unwilling to convert to academy status, it is enforced in several steps - including sacking the governors and replacing them with a hand-picked interim governing body. Ultimately the secretary of state can issue an academy order requiring a change in the school's management.
The Department for Education (DfE) sees the academies programme as its key engine of school improvement, but critics have described the process as heavy-handed and undemocratic.
The DfE plans to cut its administrative budget by £290m by 2015-16.
The document, entitled What Stops at the DfE, looks at where savings could be made.
It says forced conversions are "very resource intensive" and reveals that the government's underperformance strategy is in need of extra funds.
But despite tight department budgets, it is clear that conversions where the costs outweigh the benefits - often where there is strong opposition to a change - are still being pushed through.
The document suggests more account should be taken of a "cost-benefit analysis" in "determining the approach to academisation of underperforming schools".
But it stresses that the secretary of state does not want to see such value-for-money checks on the programme and that the changes have not been made.
It adds that ministers had expected to see some schools or heads change their mind about becoming academies as a result of high profile cases such as that of Downhills Primary School, which it cites as an example.
Mr Gove ordered the Haringey school be taken over by an academy chain, despite 94% of parents opposing the move, and claims that it was already on a trajectory of improvement when the conversion was being proposed.
Legal action was threatened as a result and teachers walked out on strike.
But the document says: "Achieving success in difficult areas has a bigger potential pay-off and is important for the reputation and reach of the overall programme but both this and forced conversions are very resource intensive."
And it warns: "If we limit the number of forced interventions there is a risk that we don't tackle the worst performing schools (which would not otherwise become academies)."
It is also clear that the DfE is seeking extra cash to ensure the forced academies programme is maintained.
It talks about "securing the additional resource needed for the underperformance strategy" and says it will not place "any arbitrary limits on forced conversion activity".
And indeed the document is peppered with references to how money can be transferred from the oversight of maintained schools so that the "increasing stock of academies and free schools can be managed".
At the same time work on a new admissions code, which the document says might prove inevitable because of various pressures, has been axed.
And oversight of boarding schools and home education is being downgraded despite civil servant warnings that there could be child protection risks as a result.
A DfE spokesman said: "Ministers are clear we will not stand by when a school is failing its pupils, and that the strong support of a proven sponsor is the best way to see rapid and sustainable improvements.
"While it is vital that government constantly considers ways to cut bureaucracy and save public money, we make no apology for prioritising improving the education of children in the country's worst performing schools."
National Union of Teachers general secretary Christine Blower said: "Despite civil servants identifying the forced academy programme as an activity that could be cut back in order to address the disproportionate cost to the public purse, this document makes clear that ideology won out over sound public policy decision making.
"It is increasingly evident that Michael Gove's pet policies are driving the education agenda at any cost.
"At a time when school budgets elsewhere are being cut is really quite an inappropriate use of public finances."
David Simmonds, of the Local Government Association, said: "In many cases, giving more flexibility to local areas to take swift action, for instance by recruiting new governors and staff, would be a better and more cost effective way of improving standards.
"Councils want to be able to intervene more quickly and effectively in poorly performing schools but are hampered by excessive bureaucracy.
"Money spent on conversion costs could be saved by enabling earlier intervention by councils who are focused on school performance rather than management structures."