The Government has been accused of making a "sustained attack" on Ireland's neutrality.
People Before Profit TD Richard Boyd Barrett was reacting to comments that Ireland would not need to hold a referendum to join NATO.
Taoiseach Micheál Martin has suggested any such move would be a policy decision of the Government.
Deputy Barrett told Newstalk Breakfast: "The Taoiseach's comments are both incorrect and also very, very alarming.
"It suggests first of all that there is a very sustained attack going on by the Government recently... to further undermine our neutrality and to try and drag us towards NATO".
He claims any membership of NATO would override current provisions, that require Dáil approval for Ireland's participation in a conflict.
"If you join NATO, you have an obligation to NATO to come to the aid of any state that is part of that mutual defence pact.
"So they would in fact be overriding the sovereignty of Dáil Éireann, and of the democratically elected representatives of the people of this country".
While Deputy Barrett says paying members of the Defence Forces 'properly' could help to boost numbers.
"We do not even have the recommended number of soldiers within our Defence Forces that we should have.
"I do think we should pay our soldiers - I do not think we need to dramatically increase our defence expenditure above and beyond that.
"And I certainly don't think that we should be, though it's clear the Government are, trying to move us in line with NATO's requirement that governments spend 2% of GDP on defence".
A former US deputy assistant secretary of defence for NATO policy has previously said the military alliance has 'an open door' for countries that want to join it.
Jim Townsend told Newstalk: "For those nations that are not in, it's a matter for those nations and the people of those nations to decide - and understand how joining the alliance might help them in terms of their own threat perception.
"How does it feel to be part of an alliance in terms of the insecurity they may feel in their region?
"Ireland would be different from Austria, be different from Switzerland.
"Nations have their own views of things - and so the alliance has an open door," he said.
