Ireland's trade union movement has taken the unprecedented step of asking human rights monitors to oversee the largest anti-G8 demonstration of next week's two-day summit amid fears that the right to protest will be swamped by Northern Ireland's biggest security operation.

The Irish Congress of Trade Unions is so concerned about the presence of thousands of police, surveillance drones, the establishment of emergency courts and a general lockdown of cities and towns that, for the first time, it has called in a civil liberties organisation to observe how the security forces treat protesters.

The Committee for the Administration of Justice (CAJ) – a group that has highlighted concerns over state repression and human rights abuses from the Troubles onwards – has confirmed it will send observers to the main anti-G8 march in Belfast on 15 June, two days before the main global political and economic summit begins in County Fermanagh.

Dwarfing some of the most dangerous set-piece events of the Troubles, the operation to protect the world's eight most powerful leaders at the picturesque Lough Erne hotel resort will deploy an extra 2,500 police officers from Britain to back up the Police Service of Northern Ireland (PSNI). A no-sailing zone will be imposed on the normally busy lough while there will also be a no-fly zone, ensuring that only police spy drones and the helicopters taking the G8 leaders from Belfast international airport will be in the air. In the Republic, the authorities have warned of a temporary shutdown in mobile phone traffic to prevent radical anti-capitalist groups and dissident republicans organising attacks.

In Belfast, the campus of Queen's University and the nearby art-house Queen's Film Theatre will be closed. The lockdown at Queen's is linked to a possible visit by Barack Obama before he flies via helicopter to Fermanagh. The university said the measures were merely designed "to ensure the safety and security of staff, students, visitors and property" during the G8 weekend.

Brian Campfield, the vice-chairman of the Irish Congress of Trade Unions in Northern Ireland and one of the organisers of the main anti-G8 rally, said the heavy security presence prompted them to call in CAJ. "Our concern would be that the security overkill would result in the prevention of a legitimate right to protest. This is the first time the trade union movement here has asked a human rights body to oversee the way a demonstration is handled by the security forces. It is a measure of our concerns that the policing and security around protests could be overzealous, and it has to be stressed the trade union movement-led protest will be entirely peaceful."

Campfield also criticised the estimated £50m bill for security. "What would £50m extra do for a county like Fermanagh if that was directly invested into the local economy instead of into this vast security operation? The majority of the G8 leaders represent and support the policies of austerity, the type of policies that have left places like Fermanagh and Northern Ireland as a whole worse off in this recession," Campfield said.

Amnesty International and Oxfam in Northern Ireland have also said they are worried about the overemphasis on security for the world leaders in Fermanagh.

Amnesty's director in the province, Patrick Corrigan, said: "At a time when the public should be encouraged to actively engage in discussions about the challenges facing the world, security measures associated with the G8 summit must not result in an unjustified narrowing of space for public participation in that debate."

Phillip Graham, from Oxfam Ireland, said the security measures and the stories surrounding them threaten to drown out important messages the world needs to hear during the summit.

"We're concerned that media attention on the policing and security around the event could divert attention from the global problems – such as the epidemic of corporate tax dodging and the hunger afflicting 878 million people – on which the G8 should be working," he said.."

PSNI commanders, including the chief constable Matt Baggott, insist they will not prevent legitimate and lawful protests. They have pointed out that the PSNI has been in constant contact with charities and NGOs, such as Oxfam, to ensure they are allowed to highlight issues such as world hunger and corporate tax avoidance.

As well as dealing with violence from the anti-capitalist fringe, which follows G8 summits around the world, the PSNI and the security services are monitoring the activities of the three dissident republican groups opposed to the peace process: the new IRA, Oghlaigh na hEireann and Continuity IRA. Earlier this year, Óglaigh na hÉireann left a car bomb near the resort and later confirmed in a statement to the Guardian that the complex had been the intended target. That attack was aborted due to a high-security presence in the county, it said.

Since then, dissident republican sources have told the Guardian that in terms of the "frontline" of the summit – Enniskillen – the terror groups have encouraged their supporters to join protesters in Fermanagh.

Security sources said they were more concerned about new IRA, Oghlaigh na hEireann and Continuity IRA attacks in other parts of Northern Ireland to exploit global media coverage while international news organisations are covering the summit.

To counter the threat from the other side of the Irish border, the Garda Síochána will deploy an extra 900 officers. They include armed members of the force's Emergency Response Unit and National Surveillance Unit. Garda and Irish Defence Forces helicopters will also be on patrol.

It is understood that members of the Irish military's version of the SAS – the Army Ranger Wing – will also be sent to the border region to deal with any attempted terrorist attacks. And, as in Northern Ireland, the Irish justice minister, Alan Shatter, has agreed to late-night and early court sittings to deal with potential troublemakers. The Garda admitted this week that it was using social media networks to gather intelligence on radical anti-capitalist groups.

Back in the north, the PSNI has also hired 170 pop-up mini-hotels that were used during the London Olympics. The so-called "Snoozeboxes" will be set up across Fermanagh to temporarily house 1,350 police officers, costing the UK taxpayer £3.8m.

A PSNI spokesman said that while everyone had the right to protest in accordance with the Human Rights Act, "police will act appropriately to ensure that there is not unnecessary disruption caused to the public by such protest".

He confirmed that the G8 summit will be the largest policing operation of its kind, with a total of 7,000 officers being deployed.