The MPs also said it said it was "essential" for Parliament to get a vote on whether to proceed if no deal was reached.
Labour MP Hilary Benn, who chairs the committee, told BBC Radio 4's Today programme: "If the government is going to make this assertion that no deal would be better than a bad deal, I think everyone would expect the government to have done some assessment."
He pointed out that farming tariffs, financial services and emergency health care in Europe were all issues that would all "fall by the wayside" with no deal.
"They should make an assessment. Because in the absence of the government explaining what mitigating measures it would take to deal with that outcome, to say that no deal is better than a bad deal is unsubstantiated," said Mr Benn.
He added there is a "balance to be struck" and "a difference between doing the work behind the scenes and making it public".