The Public Prosecution Service (PPS) said it would not be pursuing a case against a man whose palm print was discovered on the suspected getaway van. Ten workmen were killed by the IRA in the 1976 incident.
An inquest into the massacre last May was suspended after a match was found for the print. A 59-year-old man was arrested at the time in relation to the discovery.
“This is a bitterly disappointing development for the families and loved ones of those who lost their lives in this massacre,” said Mr Lunn.
“They recently had their hopes raised by the discovery of this palm print, only to now have them dashed again. I appreciate there is an evidential standard the PPS must adhere to but that will not make it any easier for the families, who have continued to campaign in a dignified and honourable manner.
“The Kingsmill massacre was one of the worst atrocities of the Troubles and I hope the police continue their enquiries so we can find the truth of what really happened and bring closure to those same families.”