Soldiers and gardaí are on standby to take over the running of the State's prisons in the event of a strike by prison officers.
Mr Sean Aylward, director general of the Irish Prisons Service, said plans had been laid to deal with a possible strike over prison reforms and cutbacks in overtime budgets.
"They [troops and gardaí] are ready to take over prisons but only in the event of a strike taking place where the prison officers refuse to provide sufficient emergency cover," he said.
Speaking on RTÉ's Morning Irelandprogramme, Mr Aylward confirmed army and garda officers had visited jails to study how they are run in preparation for a possible strike.
"It would be very irresponsible if we were not to do that," he said. "The fact is that we do not have an emergency cover agreement with the Prison Officers Association.
"They did offer to provide what they called catering and medical cover but that meant that we would not be able to unlock the prisoners or bring prisoners to and from court so a fundamental piece of security would be at risk.
"In that situation there was no choice open to the authorities but to prepare for the worst - to do anything less would be criminally irresponsible," he said.
The Minister for Justice, Mr McDowell, has demanded severe cutbacks in the cost of running the prison service - much of it relating to the €64 million annual bill for prison officers' overtime.
He has also authorised the closure of two prisons and the transfer of the management of another two to the private sector in a bid to allow the Irish Prisons Service to operate within its budget for the coming year.
The Curragh detention centre, where many of the inmates are sex offenders, is to close on January 19th, and Spike Island will close on January 31st.
However, Mr McDowell has also signalled that the decisions to close these jails may be reversed if agreement is reached with prison officers on cost-cutting measures.
Talks between management and prison officers' representatives have reached an impasse at the Labour Relations Commission.
"We are in a situation where the government has decided that it has waited long enough to achieve cost control on the pay side in the Irish Prison Service," Mr Aylward said. "It has gone on for years and years, six years of consultation, months and months, hundreds of hours of meetings and we are at an impasse.
"We have been told this year we must live within our budget, we must stop cannibalising the money that has been set aside to improve the prisons' infrastructure - to do away with slopping out and so forth - we must stop taking that money and handing it out in overtime that doesn't have to be incurred."
"We are in a crunch situation where we are making very, very slow progress and the money is very tight for this year so we feel that some of the changes we are forced to make now - the prison closures, mothballing prisons, transferring over the facilities to other managements - could, whether we like it or not, trigger industrial action and we have to be prepared for that."
A Garda spokesman said the Garda was "monitoring the situation" but could not comment on any issues surrounding training of personnel for the eventuality of a prison strike.
A spokesman for the Defence Forces said the Army was preparing for "the worst case scenario" but that there was no definite date for any deployment of personnel in prisons since prison officers had not decided to strike. He confirmed a figure of several hundred army personnel could be deployed.
Senior army and Garda officers have been involved in reconnaissance and meetings with the Irish Prisons Service for around two months and these meetings are expected to continue this week.