Mr Walker has urged MPs to help him expose further details, saying he could not say more "without incurring a much bigger risk of being sued by the NHS".
"I am still gagged. There's nearly 3,000 pages of evidence of which I have only been able to talk about a few. Those are the things I would like the health committee to expose," he said.
The BBC reported that Mr Walker had been threatened with legal action because of the interview.