Ministers have been urged to drop proposals which would allow the Home Secretary to force an inquest to be held without a jury.
The Common's all-party Justice Committee said plans in the Counter-Terrorism Bill should be withdrawn to allow time for detailed scrutiny.
The Government's proposals would allow the Home Office to appoint its own coroner to an inquest in cases which involved sensitive evidence, such as phone taps.
The Bill said the move to stop a jury inquest could be imposed "in the interests of national security," to protect the UK's relationship with a foreign power or "otherwise in the public interest".
Justice Committee chairman Alan Beith said: "The proposals in the Terrorism Bill put the choice of coroner and the possibility of excluding a jury quite wrongly in the Government's hands.
"The actions of Government bodies are regularly questioned at inquests and ministers should not be in a position to choose the coroner who will hear the case or whether a jury will be present.
"These proposals illustrate the serious dangers of piecemeal proposals to the coroners system, which it is widely agreed needs serious reform."
He added: "We are awaiting a long promised Coroners' Bill following the committee's report criticising the 2006 draft Bill.
"It would be much better to consider any changes as part of that Bill when it appears."
The committee's report said MPs were concerned that the changes proposed could see ministers choosing a coroner or excluding a jury in cases which involved state authorities such as hospitals, the armed forces, police or prisons.
