The six-week lockdown from Boxing Day will sound the "death knell" for a "tsunami" of retail and hospitality businesses - with some retailers now forced to bring forward the traditional December 26 sales, sector chiefs have warned.
From midnight on Christmas Day, all but 'essential' retailers will be forced to shut until early February.
A curfew urging people to stay in their homes from 8pm until 6am will also be in place for the first week.
No changes, however, have been made to the Christmas 'bubbling' arrangements between December 23 and 27 and schools will reopen following the festive break. The measures will be in place for six weeks but reviewed after four.
On Thursday night following intense discussions Deputy First Minister Michelle O'Neill said Northern Ireland is in a "worse position" that it has been throughout the pandemic.
Describing the situation was “quite dire”, she said the number of positive cases each day made it clear that urgent intervention was required.
The news has been met with huge dismay by retail and hospitality here, with sector chiefs warning already beleaguered business owners cannot sustain a further lockdown - particularly one which is a repeat of that in the spring months.
Glyn Roberts, chief executive of Retail NI, said the damage being inflicted on retail will be deep and irreparable.
"Make no mistake - this third lockdown will result in a tsunami of independent retailers falling and thousands more jobs being lost with permanent damage done to our local high streets," he said.
"It is profoundly disappointing that the Executive has had to take this course of action because of non-compliance of individuals and households with the Covid-19 regulations.
"This non-compliance... has now effectively shut down our economy," he insisted.
Simon Hamilton, chief executive of Belfast Chamber of Commerce, stressed that while it was accepted there was a "need for action" to tackle covid levels, it was "also worth noting that cases remained high whilst many retailers and hospitality businesses were closed.
"Knowing that closing many businesses did not impact on infection rates as hoped for previously, the Executive have once again decided to use more or less the same tactic. Do they expect a different result this time?" he questioned.
"Earlier in October, the Health Minister commented that repeated lockdowns were 'not feasible'. Yet here we are again, going round and round and round in a cycle of lockdowns."
His Londonderry counterpart, Paul Clancy, described it as "another bitter blow" to the city.
Meanwhile, Aodhan Connolly, director of the NI Retail Consortium, insisted some retailers may bring forward Boxing Day sales in order to beat the lockdown.
But he warned some cannot afford to do so, given the sector had spent £15m to make stores more covid secure.
"Some retailers may bring their sales forward, but quite frankly there is little time to do this and after the year we have had, many will simply not be able to," Mr Connolly explained.
Colin Neill, chief executive of Hospitality Ulster, said pub owners have already been "living a nightmare", adding: "Unfortunately this will sound the death knell for so many who will simply not be able to see through this enforced period.
"They won't come out the other side."
The Federation of Small Businesses NI called for "vital" support mechanisms to be implemented "more effectively" now to help the sector through the difficult months ahead.