"This is not to cast aspersions on any of the individuals concerned. But the conflict of interest involved must undermine the credibility of such a committee."
Chilcott remarks were made in a memorial lecture Monday to remember a former Sri Lankan prime minister, Dudley Senanayake.
"Dudley Senanayake would be disturbed at the many allegations made these days about corruption in politics," Chilcott said.
"He would be pleased at the existence of a parliamentary committee to investigate corruption but surprised that 22 of its 30 members are government ministers."
Chilcott's outspoken remarks came in the context of Sri Lanka's government having one of the biggest cabinets in the world especially given the small size of the country and its population of 20 million.