Police have agreed to reopen the files on several unsolved murders during the Troubles in south Armagh, Ulster Unionist MP Jeffrey Donaldson has claimed.
Ten Protestant workmen were killed in 1976 Kingsmill massacre
More than 300 murders in the area remain unsolved, including the massacre of ten Protestant workmen at Kingsmill in January 1976.
However, the Police Service of Northern Ireland said on Tuesday that there was no suggestion of any new murder investigations.
Mr Donaldson said if the chief constable did not provide resources to pursue the investigations, he would call on the government to set up an independent inquiry.
"What we're arguing is that in a number of cases in south Armagh including Kingsmill and Tullyvallen, there is evidence that the police investigations could be taken further," he said.
"We have presented some evidence to the police, they've looked at that, we've had a positive response in some cases and we are now saying that the government has no alternative.
"It is obliged in international law to pursue these investigations and secure convictions against the IRA men who were responsible for these atrocities."
Some relatives of IRA victims who met on Tuesday at Bessbrook Town Hall say they have taken a small step forward.
They say they want the same access to justice that they believe was given to nationalists.
Bea Worton, whose son Kenneth was one of those who died at Kingsmill, says she has followed high-profile cases like that of the murdered solicitor Pat Finucane with growing frustration.
"A life's a life, no matter how you look at it. My son was as valuable to me as Mrs Finucane's husband was to her," she said.
IRA gunmen killed five men in an attack on a Protestant Orange Order hall at Tullyvallen in south Armagh on 1 September 1975. No-one was ever brought to justice.
On Monday, the Police Federation said the government should fund an investigation into the murders of more than 200 police officers during the Troubles.
The group, which represents rank-and-file police, said that murdered officers and their families should be afforded the same respect as given in high-profile inquiries like the one into solicitor Pat Finucane's death.
Iona Meyer, chairman of the RUC Widows Association, said she had just as much right to find out who had killed her husband.
In April, the UK's most senior police officer, Sir John Stevens, found rogue elements within the police and army in Northern Ireland helped loyalist paramilitaries to murder Catholics in the late 1980s.
He found members of the RUC and Army colluded with the UDA in the murder of high-profile Catholic solicitor Pat Finucane, who was shot dead in front of his family at his home in 1989.
Retired Canadian judge Peter Cory has also been investigating collusion allegations in six of Northern Ireland's most controversial murders.