Despite the claim, junior defence minister Paul Kehoe says he has no plans to investigate how documents went missing, despite only being able to offer “speculative” reasons for their disappearance.

Six former members of the Air Corps have taken High Court action against the State, claiming it failed in its duty of care to protect them from the harmful effect of the toxic chemicals they used on a daily basis while working in maintenance at Casement Aerodrome, Baldonnel, Co Dublin.

All six now suffer chronic illnesses, and a toxico-pathologist has given his medical opinion that these conditions were developed as a result of their exposure to these chemicals.

The Irish Examiner understands that further cases will be brought against the State, which has denied liability in all six instances to date.

Central to all the claims is the question of whether the State took all reasonable steps possible to protect the workers. However, health and safety inspection reports published in the 1990s — at a time when all six of the claimants worked in Casement Aerodrome — have gone missing.

The Irish Examiner can reveal that, in April, a whistleblower made a protected disclosure to Mr Kehoe in which it was alleged the inspection reports were destroyed as per the instruction of an individual named in the submission to the junior minister.

The Irish Examiner previously sought the inspection reports under the Freedom of Information Act, but was told they could not be located. Despite this, the Defence Forces were able to issue this newspaper with invoices issued at the time for the 1990s inspections — but not the reports on their findings.

The inspections were carried out on behalf of former State body Forbairt.

Enterprise Ireland, which succeeded Forbairt, said it no longer held the reports, but that it sent copies of them to the Department of Defence.

The department also said it could not locate these copies of the reports.

Sinn Féin defence spokesman Aengus Ó Snodaigh recently submitted a parliamentary question to Mr Kehoe to ask if he planned to investigate why and how the documents went missing.

“The military authorities have indicated that the Defence Forces have neither a hard copy record nor an electronic copy of the Forbairt Reports,” Mr Kehoe said in his reply this week.

“The authorities have indicated that there are a range of potential causes for the loss of the reports such as the changeover of electronic recording systems in 2004 or that the reports were misplaced over time.

“However, this is purely speculative.

“It is not proposed to have an independent third party carry out an investigation into the reasons the Forbairt reports cannot be found.”

Mr O’Snodaigh said: “It is ridiculous that the minister would try to have us believe that not just one set of reports went missing, those sent to department by Forbairt in 1995 and 1997, but also those sent again by Fortbairt when they were being wound down in 1998 all mysteriously disappeared and that that’s where matter should end.”