Michelle O'Neill has accused Arlene Foster of being prepared to drive the economy "over a cliff" over Brexit.
The criticism came after Arlene Foster reportedly told a Conservative MEP a no-deal scenario is the likeliest outcome of Brexit talks.
Mrs Foster allegedly made the comments over dinner with Ashley Fox, the leader of Conservative Members of the European Parliament (MEPs).
The DUP said it wanted a deal that "works for all parts of the UK".
The comments come as Brexit negotiators are meeting to try to resolve "big issues" ahead of a crunch summit of EU leaders this week.
Mrs Foster's remarks over Brexit were reported by the Observer newspaper, which said it had seen leaked emails between government officials.
It said Northern Ireland's former first minister described Michel Barnier as "difficult and hostile".
Sinn Féin vice president Michelle O'Neill has criticised the DUP over its approach to the Brexit negotiations.
Speaking on Sunday at the annual Seán Treacy Commemoration in Kilfeacle, County Tipperary, Ms O'Neill said: "Arlene Foster is prepared to drive our economy over the cliff in pursuit of her narrow agenda with no regard for the future prosperity of the people of the north who will pick up the tab for her reckless Brexit.
"The majority of citizens north and south will not stand for any land border on this island."
'Ready for no deal'
The claims published on Sunday in the Observer newspaper state that Mrs Foster's assessment of Mr Barnier came after a disappointing meeting with the EU's chief Brexit negotiator.
Mrs Foster is alleged to have told Mr Fox the DUP was "ready for a no-deal scenario, which she now believed was the most likeliest one".
The DUP has a confidence-and-supply arrangement with Theresa May's government, which effectively means the party helps to keep the Conservatives in power at Westminster.
The deal was struck in June 2017 after Mrs May called a snap election and lost the Conservatives' parliamentary majority.
The prime minister now relies on the support of the DUP's MPs to pass contentious legislation through the House of Commons.
In a statement on Sunday, a DUP spokesperson said: "Our position remains that we want a deal that works for all parts of the UK and which preserves its constitutional and economic integrity.
"It is the arrogance and hubris of the EU which is increasing the possibility of a no-deal scenario through its desire to break up the UK."
Last week, DUP MP Sammy Wilson warned that his party will not vote with the government if it does not "keep its part of the bargain" on Brexit.
On Saturday, Mrs Foster warned the prime minister not to accept a a "dodgy" Brexit deal she will later regret.