LONDON, March 19 (Reuters) - The 1998 Northern Irish peace deal is under threat and a Pandora's box of protest and political crisis will be opened unless the European Union agrees to significant changes to the Brexit deal, a senior loyalist warned on Friday.

David Campbell, chairman of the Loyalist Communities Council which represents the views of loyalist paramilitaries, said he was calling for dialogue with the EU and Ireland to change the Northern Irish Protocol which he said had breached fundamental principles of the 1998 deal.

"We’re saying there is a window of opportunity for constructive dialogue to see if we can actually get a workable solution, and I’ve no doubt we could get a workable solution, but it does require Brussels and Dublin to return to honouring the core guarantees of the (Belfast) Agreement," Campbell told Reuters.

"If it doesn’t happen, then they are opening a Pandora’s box which leads to significant protest, to the bringing down of the Northern Ireland executive and then into a significant political crisis," Campbell said.

Northern Irish loyalist paramilitary groups told British Prime Minister Boris Johnson earlier this month that they are temporarily withdrawing support for the peace agreement due to concerns over the Brexit deal. (Reporting by Guy Faulconbridge; editing by Michael Holden)