Spokesperson for Shannonwatch monitoring group says they are "extremely concerned at this further erosion of Irish neutrality"
Activists are calling for a Dáil debate over reports that British fighter jets could shoot down hijacked planes in Irish airspace.
Earlier this week, the Irish Examiner claimed that RAF Tornado fighter jets could be called in to protect Ireland's airspace against any potential terrorist threats.
The agreement reportedly allows for the operations "in the event of a real time or envisaged threat of a terrorist-related attack from the skies".
It is claimed the agreement was reached between government departments here and in Britain several years ago.
The Shannonwatch group - which monitors foreign military use of Shannon Airport - says they are "extremely concerned at this further erosion of Irish neutrality".
In a statement, spokesperson John Lannon says a 'lack of neutrality' would prove the biggest risk to Ireland's state security.
"The US military planes and armed troops that pass through Shannon already make us a target for terrorist attacks," he argued. "And having British fighter jets patrolling our airspace heightens rather than reduces the risk of attack."
The group claims the deal appears to have been put in place by civil servants without any discussion in the Dáil.
"This is unacceptable, and we call for an immediate debate on the matter as soon as the Dáil reconvenes," Mr Lannon added.