Northern Ireland was "let down" by Great Britain following the Chernobyl nuclear disaster because officials were too busy looking after their own backyards, official files from 1986 suggested.
Many abortive hours were spent trying to contact British bureaucrats on the telephone and devolved Stormont departments were not advised about a UK-wide programme of environmental monitoring for contamination, according to the Northern Ireland Office (NIO) archives.
Vegetables, milk and water were eventually tested as a radioactive cloud arrived over Northern Ireland but the country was not properly linked into the wider system.
Emergency planners at the NIO said: "The traditional Northern Ireland dependence on departments let us down on this occasion, possibly because people in Great Britain were too busy looking after their own backyards."
In April 1986 reactor number four at the Chernobyl nuclear power plant exploded, spewing radioactive material across many parts of Europe.
Under prior arrangements the Radiochemical Inspectorate in Britain was to alert its equivalent body in Northern Ireland's administration, which had been established in 1982 under former Northern Ireland secretary Jim Prior.
The NIO said: "This procedure failed to operate in the Chernobyl incident.
"In any future emergency Northern Ireland should be part of a UK plan which at the end of the day must be able to identify the problems and provide the necessary solutions."
The following day the radioactive cloud from the Russian reactor reached Northern Ireland. Monitoring of milk, water and air took place. Samples of vegetables and grass were sent for testing and the importing of fresh meat from Eastern Europe banned.
But the Agriculture Department in Northern Ireland was not informed of the position in other countries; this could be a particular problem in relation to the Republic of Ireland, the files said.
The report said if food coming from the Republic across the land border was affected by a disaster the department wished to know so it could act responsibly on imports.
No Stormont department had been designated to take the lead because contingency plans did not cover an accident happening outside the UK.
The NIO said: "Similarly the absence of a lead department in Northern Ireland meant that co-ordination was unsatisfactory and undoubtedly led to delays in the processing and co-ordination of information and delays in the issue of public statements."
The emergency planning branch said too much was left to the initiative of scientists.
"Certainly in the few early days over the holiday weekend of 2-5 May co-ordination depended upon staff knowing each other personally and speaking between themselves as they thought necessary.
"Northern Ireland departments should have been advised on May 1 of the DoE (GB) plans to extend environmental monitoring.
"This was not done and even on May 3 DoE (GB) did not apparently contact any Northern Ireland department relative to the national programme of monitoring.
"In the Chernobyl incident Northern Ireland was clearly not properly linked in to the national system.
"It is reported by DoE NI that many abortive hours were spent trying to get in touch with officials in Great Britain on the telephone."