Loyalists have held talks with the Northern Ireland Office (NIO) about the Irish Sea border and any threat it may represent to the Union.
The 90-minute meeting was described as "forthright and hard-hitting", with four NIO officials told of the "anger on the streets" in loyalist areas.
The delegation from the Loyalist Communities Council (LCC) included Winston Irvine, Jimmy Birch, Robert Williamson and David Campbell.
The LCC is an umbrella organisation representing loyalist groups including the UVF, UDA and Red Hand Commando,
It said it was "briefed on the implementation of the Northern Ireland protocol" by NIO permanent secretary Madeleine Alessandri and three other officials.
The NIO did not respond to a request for comment about the meeting, which took place via Zoom because of the coronavirus pandemic.
Mr Williamson said: "It was forthright and hard-hitting. People spoke their minds. It was important for the NIO to be told the feeling in loyalist working-class estates. There is a lot of fear that our identity is being diluted. There are concerns about empty supermarket shelves and lorries queued at ferry ports."
The LCC said the Government must act "to ensure there would be no actual or perceived diminution in Northern Ireland's constitutional position".
The delegation said their rights must be protected under the Good Friday Agreement.
"Unionist politicians have been slow to do that. The Good Friday Agreement should not be a green document. There are a million unionists in Northern Ireland and the agreement is there to protect us too," Mr Williamson explained.
On the issue of the Irish Sea border, the LCC urged loyalists to "remain calm during this transition phase".
But it also warned the NIO that it would be "monitoring" the treatment of Northern Ireland citizens under the new dispensation and, "if necessary", would "consider sponsoring legal action to protect the position of unionists".
The LCC also asked the NIO to ensure that new US President Joe Biden "was briefed on the need for impartiality and respect for the majority position in Northern Ireland when it comes to dealing with NI-US issues".