TUV leader Jim Allister has accused PSNI Chief Constable George Hamilton of "playing politics" by warning of an increased dissident republican threat in the event of a hard border.
Mr Allister said that any Brexit deal should not be agreed on the basis of "a terrorist threat".
Appearing in front of the Northern Ireland Affairs Committe this morning, he said: "Have we really got to the point where we are building our politics and our international agreements on pandering to terrorism?"
The North Antrim MLA said George Hamilton had been "talking up the threat from terrorism as a reason for not having a proper Brexit."
Lady Sylvia Hermon refuted the suggestion the chief constable had been playing politics, and said it was "an appalling thing to say".
DUP MP Sammy Wilson, also appearing before the committee this morning, dismissed a warning from the head of the north's civil serice that a no-deal Brexit could lead to a sharp rise in unemployment as "a scare tactic".
Mr Wilson said: "I have no doubt this was written for a political motive."
When the letter arose in conversation again, an animated Mr Wilson said: "We've got from David Sterling in his letter, it's a scare tactic."
When Ms Hermon interrupted, Mr Wilson said: "I don't care if he's head of civil service or Santa Claus, it really doesn't matter, the fact of the matter is, he's got it wrong."
Mr Wilson said he finds it difficult to believe that business, retailer and farming union members in Northern Ireland support Theresa May's Withdrawal Agreement.
"I find that rather odd," he said.
"Let's just take the Ulster Farmers Union, if they had read the agreement they would actually find that state aid rules applying to Northern Ireland would mean that the EU could cap that support, in accordance with what they saw as the appropriate policy.
"As far as businesses, I do find it very difficult to understand why Northern Ireland businesses who export around the world would wish to be excluded from UK trade deals in the future."
Lady Hermon asked Mr Wilson about quotes he gave to the BBC last week where he said a backstop could be agreeable if it had a time limit.
"The question that was asked was, would the DUP accept current withdrawal agreements, I made it clear no we wouldn't," Mr Wilson said.
"The issue was the separate backstop arrangement for Northern Ireland, and the fact that the UK couldn't get out of those arrangements without the assent of the EU.
"Regardless of the mechanism, the outcome was important, and the outcome was no longer would the EU be able to dictate to the UK the arrangements that would persist for UK as a whole and Northern Ireland and the EU, and the way of doing that was to have an end date for backstop.
"The point I was making was, the backstop could be removed if they didn't want to have the Withdrawal Agreement totally destroyed, you could impose a time limit on backstop."
Lady Hermon also asked if the DUP were willing to face the consequences of a no-deal Brexit.
Mr Wilson replied: "If we finish up with a no-deal it will be a result of the intransigence of the EU.
"We have made it quite clear all along that we wish to have a deal, but they have to have a deal which has the support of people within the House of Commons.
"You can't expect the government to cave in because the alternative is no deal."
Kate Hoey asked Mr Wilson if there is any truth that the Northern Ireland business leaders saw the Withdrawal Agreement before people in the House of Commons.
"I think that maybe they were given a precis of what was in the agreement, designed to play down bad parts of it, and emphasise the parts that would be attractive to them.
"One thing I do know is that they made their pronouncements before the 587-page document was available, they must have made it on a basis of a briefing they were given, no one should do that especially when one party has an interest that it's skewed in a certain way."
