The Quality Assurance Agency says it has no knowledge of the teaching quality at two-thirds of the private institutions to benefit from state-backed student loans funding.
The QAA, which is responsible for safeguarding standards in the sector, made the statement to Times Higher Education as it emerged that private providers are seeking admission to the Universities and Colleges Admissions Service and to Universities UK, the vice-chancellors' body that represents the sector in negotiations with the government.
Minutes from a meeting of the Interim Regulatory Partnership Group, set up by the Higher Education Funding Council for England and the Student Loans Company to look at transition to the new system, state: "Both Ucas and QAA reported that alternative providers were seeking admission to their organisations and both were looking at their membership models. Similar approaches were being received by UUK and the Committee of University Chairs."
A UUK spokesman would only say: "As a matter of policy, we don't publicly discuss membership applications or terms."
Despite the suggestion that private providers are seeking greater involvement with the sector's key bodies, the private sector's overall engagement with the QAA appears to be limited.
The QAA said that it presently has 11 private subscribers (five with degree-awarding powers) subject to "institutional review", the same assessment to which their Hefce-funded degree-awarding counterparts are subject.
But state-subsidised SLC funding went to students at 94 private providers in 2010-11, the QAA said.
At present, students at private providers are allowed access to SLC funding where the provider's courses are "designated" by the government - nominally by the business secretary, Vince Cable.
Courses can only be designated if they are validated by a recognised UK awarding body, typically a Hefce-funded university - which the government says provides quality assurance.
The higher education White Paper contained plans to make all providers of designated courses subscribe to the QAA. But the higher education bill that would have created such legislation appears to have been shelved.
THE asked the QAA, which says it has "good knowledge" of the private sector, what proportion of private providers with designated courses it assessed.
A spokeswoman said there were 94 private providers with designated courses listed by the Department for Business, Innovation and Skills in 2010-11.
The spokeswoman said that of those private providers, six were "due to be assessed in the next cycle" of the QAA's institutional review.
She said another 25 of the group of 94 are "scheduled for an educational oversight review", the form of review that private institutions must undergo if they wish to recruit overseas students.
THE asked whether it was thus fair to say there are 63 private colleges in receipt of state-backed loans where QAA has no knowledge about teaching quality.
Stephen Jackson, director of reviews at the QAA, said in a statement of response: "Yes, based on the information we have available.
"The latest BIS list of private providers designated for SLC funding gives the names of 94 colleges and other providers.
"Thirty-one of these are in QAA's sights, either as subscriber organisations...or as applicants for educational oversight. The remainder have no relationship as yet with QAA."
THE asked if "educational oversight" was of equal rigour to full institutional review.
Dr Jackson said: "We will be carrying out the same assessment for private providers as we do for publicly funded colleges delivering higher education.
"Institutional review is our assessment of bodies with degree-awarding powers.
"Educational oversight is our assessment of providers of higher education programmes validated by a degree-awarding body."
As THE has reported, the list of designated private providers includes institutions such as the Delamar Academy, a make-up school, and Mattersey Hall, an Assemblies of God Bible College, as well as better-known names including BPP University College, which is a subscriber to the QAA.
While Hefce-funded universities are capped on the number of students they can recruit in order to control costs to the taxpayer, private providers are not subject to such caps.
Sally Hunt, the University and College Union general secretary, said private institutions "can provide courses on the say-so of the secretary of state, recruit as many students as they like, do not have to answer to the QAA and the taxpayer picks up the tab".
She said of private providers' apparent wish to join institutions such as UUK and Ucas: "This rush by private providers to immerse themselves in the respected public sphere of our higher education system must be resisted until the private sector is properly controlled and regulated.
"Only by keeping them at arm's length can we protect the reputation of UK higher education as a whole."