Northern Ireland businesses "simply cannot cope" with a no-deal Brexit, according to Confederation of Business Industry (CBI) director Angela McGowan.
Ms McGowan told the BBC "no country in the world will want to invest in Northern Ireland if it is thrown out of Europe" without access to EU markets.
She was among a delegation of Northern Ireland business leaders who meet the DUP over the EU withdrawal deal.
The DUP has said the agreement is "worse than no deal".
The party has said that its 10 MPs will vote against Prime Minister Theresa May's proposed EU deal in Parliament.
It has led to a rift with business and farming groups in Northern Ireland who have urged the DUP to support the deal.
Speaking after meeting about 30 business and farming leaders, the DUP leader Arlene Foster said she reiterated her party's opposition to the Brexit withdrawal agreement.
"It was a very useful meeting," Mrs Foster said.
Mrs Foster said the media was trying to "put a wedge between the political party and the business community".
She added that the meeting gave to DUP an opportunity to update the business community about a meeting between the party and the Home Secretary regarding Northern Ireland's future labour market.
'State of chaos'
As well as the CBI, other business groups that visited Stormont on Monday include the Northern Ireland Retail Consortium, the Chamber of Commerce and several food and drink umbrella groups.
The business delegation also met four Stormont parties that oppose Brexit - Sinn Féin, the SDLP, Alliance and the Green Party.
Earlier in November, the BBC learned the DUP had asked the Chamber of Commerce to facilitate a meeting with business groups, to explain its opposition to the deal.
DUP MP Sammy Wilson had accused businesses backing the deal of being "the puppets of the Northern Ireland Office".
After the meeting, the delegation said the meeting was "very constructive" but rejected Mr Wilson's claim.
"What was expressed was that we're both big enough and ugly enough to work through the rough and tumble of Northern Ireland politics and no hurt was taken on either side," said Aodhán Connolly, of the Northern Ireland Retail Constortium.
"But I think it's safe to say we're nobody's puppets," added Glyn Roberts, from Retail NI.
He said: "I think today was useful, that it was the first formal sit-down meeting with the DUP. I think it was very good, it was very constructive.
"But, you know, I think the key parliament we need to be at is not actually this one, it's actually over in Westminster and all of us need to be engaging with the Labour Party, with the Lib Dems and with those other backbenchers who are presently voting against this deal."
Earlier, speaking to the BBC's Good Morning Ulster programme, Ms McGowan said leaving the EU without a deal was "not an option" for the business sector and she would try to present real-life case studies to back their position in Monday's meeting.
"All I can do is do my best to put the honest evidence on the table that companies simply cannot cope with no deal," the CBI director said.
"We're talking about people; neighbours; your relatives being put out of jobs - companies cannot cope with this uncertainty."
She claimed a chaotic Brexit could disrupt food and medical supplies.
"We'll be forced into having emergency bilateral arrangements with the EU to try and cover things like getting enough medical supplies," she said.
"That is no way to run a country and I don't think anybody who went out in June 2016 voted for that."
'No more negotiation'
The DUP opposes the draft agreement because of the backstop, which aims to avoid a hard Irish border.
It would see only Northern Ireland stay aligned to some EU rules if it took effect.
The UK government and the EU insist it is only an insurance police in the event that there is no breakthrough by the end of the transition period.
European Commission President Jean-Claude Juncker has said there will be no more negotiation on the Brexit agreement, saying is the "best deal for Britain".
"This is the only deal possible. So, if the House (of Commons) says no, we would have no deal," said Mr Juncker.
Taoiseach (Irish prime minister) Leo Varadkar also said the Brexit deal agreed between the UK and EU at the weekend was the "best deal that was available to the United Kingdom".
Speaking on Monday, he argued that Sinn Féin MPs should take up their seats at Westminster before December's vote on the proposed Brexit deal.
He said if they are not willing to take up their seats, or feel they cannot because of their policy on abstention, they "have the option of resigning", RTÉ reported.
Mr Vardkar said that if Sinn Féin representatives resigned, it would allow people in Northern Ireland decide whether or not they want to "have a say" when the vote comes to Westminster.
In a statement responding to the taoiseach's comments, Sinn Féin leader Mary Lou McDonald said the party has no intention of standing aside and "abandoning our mandate".
"If the taoiseach and Fine Gael think Irish politicians should take seats in the British parliament, they should seek a mandate for that, stand candidates in the Northern elections, and stop hurling from the ditch," she said.