The claims were made by a number of former Irish army officers and soldiers who told the Irish Examiner it became apparent in the early 1980s that the Israeli Defence Forces (IDF) and the South Lebanon Army (SLA), an Israeli proxy operating inside Lebanon, were able to react “too quickly” to communications as Gaeilge.

As many Israelis and the opposing Hezbollah could speak English, the Irish troops used Irish to pass sensitive information between their peacekeeping units.

It was similar to US operations against the Japanese in the Second World War when they used Navajo to prevent the enemy intercepting communications.

One former senior Irish officer said, in hindsight, it should not have surprised them that the Israelis would “quickly cop on” and either source Gaelic-speaking operatives or train their own.

An ex-soldier who undertook a number of tours in Lebanon said he met a couple of IDF members with pronounced Irish accents.

A former middle-ranking officer who also served with the UN in Lebanon said he got instructions from a senior colleague to be careful when talking in Irish and be more cryptic if possible as the Israelis seemed to know what they were saying.

He said one of his NCOs had told him he was “absolutely positive” he had seen an IDF member who had previously served with the Irish Army.

It is unclear if these members were called up for translation duties, or if the IDF or Mossad, Israel’s secret service, sent operatives here to learn Irish.

Israel has previously provided its military with fake Irish passports for clandestine operations. In 2010, agents working for Mossad used fake Irish passports to enter to Dubai to assassinate Palestinian commander Mahmoud Al-Mabhouh.

To prevent anyone eavesdropping on conversations, the Irish army introduced encrypted radios in the mid-1980s, and updated protection systems in 1994.

The Israeli embassy was asked to comment on the allegations made by the former Irish soldiers. In a statement, it said: “Unfortunately, we do not have any information pertaining to this matter.”

The Irish army has been deployed to South Lebanon on three separate occasions. The first deployment was between 1978 and 2001, with another between 2006 and 2007. A third deployment is ongoing since May 2011.