Shadow health secretary Andy Burnham denied putting pressure on the health watchdog to play down concerns over a scandal-hit hospital trust where mothers and babies died.
The Care Quality Commission (CQC) has been under fire over allegations it covered up its failures over investigations into the Morecambe Bay trust.
The Sunday Telegraph claims it has seen documents which revealed the CQC was intent on suppressing negative publicity and was under pressure from Labour ministers in the run-up to the 2010 election.
But Mr Burnham, who was health secretary at the time, said he denied the central allegation that he put pressure on the CQC to cover-up information about Morecambe Bay.
He said it was "fundamentally disproved" by the decisions he took to actively identify problems at hospitals during his time in office.