The proposed Historical Inquiries Unit (HIU) must hold the IRA to account for no-warning car bombs, according to a UUP MLA.
Former party leader Mike Nesbitt said the HIU should investigate Troubles-related injuries as well as deaths.
The Northern Ireland Office (NIO) last week gave the main parties sight of their proposed consultation document on dealing with the past, including the setting up of the new bodies proposed in the Stormont House talks.
As proposed, the HIU will be a parallel police force, with the same powers of investigation and arrest as the PSNI.
However, it will not be able to hold the IRA to account for thousands of injuries inflicted through its campaign of no-warning car bombs.
Mr Nesbitt said: "Police records suggest there were some 15,000 bombings during the Troubles, leaving many thousands with life-changing injuries, but in the cases where no one died as a result of the explosion, there will be no HIU investigation.
"So, if you went out armed to the teeth intending to cause death and destruction and ended up dead, your family are entitled to a full investigation by the HIU.
"But if you went to the shops for a newspaper and lost your legs in a no-warning bomb explosion, the HIU don't want to know.
"This is utterly perverse.
"The IRA and the other terrorist organisations must be held fully to account for their actions."
The NIO had not responded to a request for comment by time of going to press.