The DUP position on a no-deal Brexit is "all over the place", the Ulster Unionists have claimed.
UUP leader Robin Swann said his rivals' stance changed depending on who was speaking.
Mr Swann claimed DUP MP Sammy Wilson was content for the UK to leave the EU at the end of October without a formal withdrawal accord, while Mr Wilson's Westminster colleague Jeffrey Donaldson wanted to see a deal.
The UUP chief said his party was "clear" in its opposition to no deal.
"It's dangerous for Northern Ireland, it is politically irresponsible for the UK to go down that line and it's something we have been very clear on - we need a deal to get out of the EU," Mr Swann said at Stormont.
On the DUP position, he said: "I think it depends who you are actually listening to in the DUP. We have got all measures.
"Sammy Wilson is content to go out with no deal, Jeffrey Donaldson, he says somewhere along the same page as ourselves that he wants to see a deal before the exit is done, so the DUP seem to be all over the place.
"We are very clear that we need a deal to exit."
Mr Swann was speaking after meeting newly appointed Northern Ireland Secretary Julian Smith at Stormont House.
DUP MP Gavin Robinson, who also met Mr Smith yesterday, rejected Mr Swann's assertion. He said the DUP wanted a "sensible" deal and was approaching Brexit on a "problem-solving basis".
"We want to have a deal, we want to have a deal that recognises Northern Ireland's unique challenges but is also of benefit to the United Kingdom as a whole," he said.
"So our focus throughout this over the last number of years, looking at draft withdrawal agreements and discussing with the Government, is getting a deal that suits Northern Ireland and the rest of the United Kingdom.
"That's where the focus lies but at the end of this we need to honour the result of the referendum," Mr Robinson added.