It is the first such inquiry to be conducted under the QAA's revised "whistleblower" process for investigating concerns about academic standards and quality. It follows the closure of 16 courses and 26 full-time equivalent redundancies at the institution, which is part of the University of the Arts London.
The QAA said it had received three student complaints relating "to restructuring at the University of the Arts London and its alleged detrimental effect on students".
"(After) an initial inquiry, the case is now under full investigation," added Stephen Jackson, the QAA's director of reviews.
The agency investigates concerns when it thinks they might indicate "serious systemic or procedural shortcomings by the institution or institutions involved".
Times Higher Education understands that the complaints involve concerns about contact time, staff redundancies and levels of supervision. They relate to current courses and ones that have recently ended.
In 2009, Paul Simpson, course director of a surviving LCC course, the BA in public relations, resigned after raising concerns about the lack of teaching support for students.
Plans for further redundancies and course closures have been announced under a programme that puts 20 full-time equivalent posts at risk and will cut the work of associate lecturers by 700 hours in 2011-12.
There have also been concerns about management interference in the university's student newspaper, Arts London News.
An article about the investigation was pulled from the 17 March print edition of the paper after Paul Charman, the head of journalism, read the story and raised legal concerns.
In an email seen by THE, he says comments in the article "might be held to prejudice the outcome of the investigation, which has all the weight of civil proceedings...The QAA has extensive powers, even to the extent of closing the university."
However, after the LCC's University and College Union branch questioned why the story had been spiked, a different version of it ran on the paper's website on 21 March.
THE has seen both versions of the article and could identify no obvious legal risks associated with either. The QAA does not have the power to close a university.
The watchdog said it could not compel universities to take any action in response to its findings, but it informed funding chiefs of its findings as well as publishing them.
A spokeswoman for University of the Arts London said it would not be appropriate to comment on the investigation before it concluded.
On the story that was pulled, she said: "The university understands from colleagues at LCC that they asked Arts London News to postpone publication to provide an opportunity to address inaccuracies in the story."
Gary Horne, UCU chair at the LCC, said: "It is sad and disturbing that the college is subject to an investigation. This is a very rare event and indicates its seriousness. This investigation arises from the initial closure of the School of Creative Enterprise and most of its courses."
In the latest National Student Survey, only 21 per cent of students studying marketing at the university were satisfied with their courses.