Senior DUP figures last night dismissed dire warnings contained in a secret Whitehall dossier of "direct action" and border protests after Brexit.
Party leader Arlene Foster MLA and Brexit spokesman Sammy Wilson MP spoke out after the leak of a Cabinet Office document which suggested a no-deal Brexit could mean a hard Irish border, massive trade disruption, roads blockaded, intensified smuggling and political unrest in Northern Ireland.
The document, published by the Sunday Times, also warned the UK could be hit with a three-month "meltdown" at ports, and shortages of food and medicine.
East Antrim MP Mr Wilson said he regarded the selective leaking of parts of the Operation Yellowhammer planning document as indicative of a "climate of hysteria" which has intensified as the Brexit deadline nears.
And party leader Arlene Foster said the leak was an attempt to undermine the Prime Minister.
"This leak has come at a time when the new Prime Minister is planning to speak to EU leaders as we approach the UK leaving the EU in October," she said.
"Attempts to undermine these talks with EU negotiators are not in the national interest.
"It is important that we use the remaining time to work on getting a deal, with the best possible outcome for the UK. There is still time for a deal but it requires an attitude change in Dublin and Brussels.
"The backstop and any creation of an Irish Sea border would undermine the Union, and indeed it will be catastrophic for our economy.
"As a party we will continue to support the Government to work towards a deal that respects the referendum result and maintains the constitutional and economic integrity of the UK," she said.
Mr Wilson claimed cynical people in London were using Northern Ireland as propaganda to try to stop Brexit and overturn the 2016 referendum result.
"There is a climate of hysteria building up," Mr Wilson said.
"If you look at the kind of predictions that have been made - such as that we will be unable to sell our milk... well, there is a willing buyer just across the border, because their butter industry, their cheese industry, tens of thousands of jobs, depend on Northern Ireland milk.
"It's the same with sheep farmers. The UK Government has already said if there are short-term difficulties, they will introduce measures to mitigate them, ensuring that there is no disadvantage to producers. When it comes to the movement of goods across borders, the Irish Finance Minister has made it clear there will be no posts along the border at all."
Asked if he gave any credence to fears of a return to violence in Northern Ireland as a result of a no-deal Brexit, Mr Wilson said: "I think that is totally irresponsible, because it does whip up fear among communities, especially along the border, who suffered for years and years.
"To me, that is one of the most cynical aspects of this debate.
"People are being used as pawns, and their fears are being played upon."
He said fears border posts would be attacked by republicans were groundless - as none would exist.
According to the documents, petrol import tariffs would also "inadvertently" lead to the closure of two UK oil refineries, while protests across the country could "require significant amounts of police resources" in a no-deal scenario.
Sinn Fein's deputy leader Michelle O'Neill said Ireland had been voicing concerns for months: "These reports are no surprise to those of us on this side of the Irish Sea who have been voicing our very real concerns on the consequences of a no-deal Brexit for a considerable period of time directly with the British Government and the European Commission," she said.
"The island of Ireland faces its biggest and most profound challenges in a generation as the threat of a no-deal Brexit becomes a growing reality in the immediate time ahead.
"The consequences of a no-deal Brexit will result in a hard border which threatens our hard-won peace and undermines the political and economic progress of the past 21 years enjoyed across the whole island, but particularly in border communities which have been transformed. It will have devastating effects for the island of Ireland and our people, businesses, farmers, workers and communities.
SDLP leader Colum Eastwood said Boris Johnson's plans for a no-deal Brexit on October 31 were "a threat to stability and prosperity on this island".
He added: "This British Government, far from sending a clear message to Brussels, is sending a clear message to people and businesses in Northern Ireland - they are willing to sacrifice our economic, political and social wellbeing to please rabid nativists in their own ranks."
Michael Gove - the minister responsible for no-deal planning - insisted Yellowhammer represented a "worst-case scenario".
A Downing Street source said: "This document is from when ministers were blocking what needed to be done to get ready to leave and the funds were not available. It has been deliberately leaked by a former minister in an attempt to influence discussions with EU leaders."
Former NI Secretary Owen Paterson claimed the leak was an example of the "Establishment" plot to "sow fear in people's minds".