In a report on the BBC's annual accounts, published last week, the committee said the trust's statements about the progress of VoD joint venture Project Kangaroo were “at best, incomplete and, as a result, potentially misleading”.
It also accused the regulator of a “significant failing” because it did not reprimand the BBC after the corporation failed to provide audience reach information it had promised.
The damning remarks follow shadow culture minister Ed Vaizey's promise that a Tory government would radically shake up the way the BBC is regulated - with a new chairman to “cheer-lead” for the BBC and a clearer separation between the BBC and its regulator.
The select committee report also revealed details of chairman John Whittingdale lambasting the trust in a closed oral evidence session in July last year.
“Is there not a real problem here that you, as the Trust, have put a joint submission to Ofcom proposing something where you may then have to arbitrate over any complaints which are subsequently raised? You are trying to fulfil two functions,” he said.
But the trust rejected the select committee's accusations. Chairman Sir Michael Lyons said it offered “quicker decision-making, more challenge of BBC plans and a much more open approach” than the previous arrangement.
“The BBC Trust is much more than a regulator. We can celebrate BBC achievements where that is justified - but also take swift and decisive action when we see things going wrong,” he added.