The government has been urged to think again about its decision not to appoint a chief coroner.
MPs will debate the public bodies bill later today.
It contains provisions to transfer some of the chief coroner's statutory powers to the lord chief justice and the lord chancellor, with a ministerial board overseeing the non-judicial aspects of the service provided in England and Wales.
The last Labour government set up the post of chief coroner, a judicial office-holder who would lead reform, introduce national standards and oversee a new appeals system.
However, ministers have said the new post will cost £10m to set up, with annual running costs of £6.5m.
Shadow cabinet office minister Michael Dugher said honouring the commitment to create the office of chief coroner is the first test of the new military covenant.
"To fail in their duty to meet that test, would make a mockery of the government’s assurances of greater support for our military and their families," he said.
The Royal British Legion said the establishment of a chief coroner's office was critical to improving the working of the inquest system in relation to military inquests.
These include oversight and monitoring of investigations into service deaths; compulsory training for coroners carrying out military inquests; and new rights of appeal for families throughout the inquest process.
INQUEST, a professional advice service on contentious deaths and their investigation, has produced an alternative timetable for full implementation of the reforms with the Royal British Legion.
"Parliament recognised that the inquest system is in urgent need of reform when it passed the coroners and justice act just two years ago with cross-party support," said INQUEST co-director Helen Shaw.
"The act created the framework for updating our coronial system so that it is fit for the 21st century.
"We cannot allow short term financial considerations to throw the years of thoughtful work reflected in the legislation onto the so-called 'bonfire of the quangos.'
"Each year tens of thousands of bereaved families are forced to endure lengthy delays and an archaic, unaccountable and inefficient system which also leaves the coronial service unable to fulfil its vital function of preventing unnecessary deaths."
Chris Simpkins, director general of The Royal British Legion, said: "We believe this decision would be a deep betrayal of bereaved service families.
"It may be that ministers have not appreciated the ramifications of such a decision on bereaved armed forces families."
Dods Parliamentary Communications Ltd