The families of three Scottish soldiers murdered by the Provisional IRA at the beginning of the Troubles in Northern Ireland have launched a campaign to expose their killers.

The Three Scottish Soldiers Campaign for Justice group wants three suspects it says are still living openly in the Irish Republic brought to justice.

The campaign will be seen as a case of “turning the tables” on recent moves by the families of republican activists shot dead by the security forces to bring soldiers and police officers through the courts over Troubles-related deaths.

Fusiliers Dougald McCaughey, 23, John McCaig, 17, and his brother Joseph, 18, were the first soldiers to be killed while off duty during the Troubles after the PIRA decided to escalate its armed campaign.

They were lured into a “honey trap” by women who befriended them in the centre of Belfast then took them to a house party in the north of the city, where an IRA unit shot them dead. Their bodies were left on an isolated road overlooking Belfast and were found by children.

At the launch of the campaign in Glasgow on Tuesday, the group said the families of the soldiers had the right to know the identities of the suspects and see the British state attempt to have them extradited to the UK.

David McCaughey, a relative of Dougald McCaughey, said: “This is a scar in my family that has never healed. I made promises to family that are no longer living that I would never let these boys be forgotten, I will never break that promise. I suffer from ill health due to cancer. I now know that if my health took a turn for the worse that there are good people in this campaign working to fulfil my original promise.”

The campaign is backed by London-based law firm McCue & Partners, which has supported relatives of IRA victims killed and injured with Libyan-supplied weapons during the Troubles. The firm has provided support for their fight for compensation from the Libyan government over the late Colonel Muammar Gaddafi’s supply of arms and explosives to the PIRA.

Matthew Jury, a managing partner at the law firm, said: “It is a terrible injustice that, time and time again, UK veterans are singled out for prosecution while IRA terrorists walk free. In this case, the authorities know the names of the soldiers’ killers, but still nothing is done. All the while, their families and loved ones are kept in the dark. They have the right to know the truth and to see those responsible brought to justice.”

Last month it emerged that two former soldiers will be charged with the killing of the Official IRA leader Joe McCann in Belfast in 1972.

They are known as Soldier A and Soldier C and are believed to have been paratroopers. The pair will be the first former members of the British military to be charged with murder during the Northern Ireland conflict.

McCann’s family claim he was shot in the back by members of the Parachute Regiment at a time when he was one of the most wanted republican gunmen in Northern Ireland.

McCann sided with the Marxist Official IRA when the IRA split in 1969. He took part in the Official IRA gun battle with the British army in the Lower Falls district a year later.

In 1971, McCann led an Official IRA unit that temporarily held back 600 British troops who had flooded into the Market district to arrest local men without trial when the late Edward Heath agreed to unionist demands for internment.