The government's "Soviet-style" interference has wrecked its own ambitions of creating a free market for post-16 students, a college leader has warned.
By favouring academies above all other providers, education secretary Michael Gove has actually stifled competition, according to James Kewin, deputy chief executive of the Sixth Form Colleges' Forum (SFCF).
While no sixth-form colleges have yet bitten the bullet and applied to become an academy, Mr Kewin said that many are still considering making the move because of short-term "desperation" for extra funding.
"If it really was a free market the government wouldn't be interfering as they are, supporting certain players while chipping away at others," he said. "We would embrace an unrestricted free market, but that's not what's happening."
Arguing that sixth-form colleges outperform schools in terms of success rates and Ofsted inspection grades, Mr Kewin said that the "beleaguered" sector feels marginalised by the Department for Education's strategic focus on the academies programme.
"I am not sure how many more cuts as a sector we can take," he said. "If a college does decide to convert to academy status, it will be for the wrong reasons, because of the short-term benefits. It will not be down to strategic thinking; it will be driven by desperation.
"The worst-case scenario would be that they lose the kudos of being a sixth-form college," he added.
In February, TES revealed that the Norvic federation of 15 sixth-form colleges in the North East had decided jointly to explore academy conversion. But there is still some hesitancy: as yet, none of its members has applied to make the transition.
An SFCF report published this week ahead of the forum's annual conference in Cambridge argues that, despite enrolling students with lower levels of prior educational attainment from less affluent backgrounds, colleges still outperform other kinds of post-16 providers.
Its latest research argues that the current success rate for sixth-form college students is 84 per cent, compared with 80 per cent in academies and other schools with sixth forms.
It also cites Ofsted's annual report for 2010-11, which revealed that 70 per cent of schools were rated good or outstanding, compared with 78 per cent of sixth-form colleges.
This follows a National Audit Office report last year, which concluded that colleges outperform schools in most areas, despite receiving significantly less funding.
Colleges are also judged more harshly by Ofsted, the SFCF report argues. It found that more than 300 schools have a worse success rate than the lowest performing sixth-form college, but many of these were rated outstanding for their post-16 provision.
But the SFCF has warned that while the DfE has been keen to promote the establishment of new free schools, there has been no push to create new colleges.
"Sixth-form colleges do not require special treatment from the government to maintain their high standards," Mr Kewin said, "but they do need to be funded, inspected and supported in the same way as other providers operating in the 16-18 market.
"It makes sense to invest in our highest performing and most efficient sector. Failing to do so will mean losing some of the institutions that have successfully acted as engines of progression and social mobility in this country for more than 40 years."
Colleges v schools
Proportion of institutions rated good or outstanding:
78% Sixth-form colleges
Overall student success rates:
84% Sixth-form colleges
80% Academies and other schools with sixth forms.