The UK Government has been accused of continuing to "play reckless games" over Brexit.
The comments from Sinn Fein MLA Declan Kearney come after the NI Affairs Committee at Westminster slammed the approach to post-Brexit trading arrangements, which has left businesses ill-prepared for the end of the Brexit transition period on December 31.
Mr Kearney said the committee's report confirms concerns about the Government's failure to provide clarity or certainty.
"It has been increasingly obvious that this British Government is neither properly focused upon, or concerned about, addressing the lack of detail required by businesses," he said.
"I am not surprised this British parliamentary affairs committee remains to be convinced the current British Government fully understands its political approach provides neither the clarity nor the detail required by the business community in the north."
Mr Kearney also criticised the Government for not seeking an extension of the transition period as "absolutely wrongheaded".
Ulster Unionist Peer Lord Empey was also highly critical of the Government's stance.
"Less than six months before the end of the transition period, it is distressing to hear Cabinet ministers denying that there will be a border in the Irish Sea," he said.
"This attempt to hide from the reality is doing no service to business or the general public.
"There will be a border in the Irish Sea."
Alliance MP Stephen Farry said the report posed major challenges to the UK Government.
"MPs with different positions on Brexit share common ground in expressing deep concern at the pace of preparation and provision of information regarding the operation of the Northern Ireland Protocol," he said.
"With just over five months to go, the UK Government need to provide detailed information on how checks are going to operate, and ensure the necessary staffing, infrastructure and IT systems are in place.
"There is a real risk of chaos at the beginning of January."
SDLP MP Claire Hanna said businesses will face additional barriers to trade with Britain if the UK Government doesn't take action on its pledge to secure "unfettered access" to the British market.
"The report reflects on the failure of Boris Johnson's Government to engage with the fundamental contradictions of their position," she said.
"To continue to boast about unfettered access to the GB market for Northern Ireland businesses without addressing the need for export and exit summary declarations under EU customs rules is fundamentally dishonest.
"As it stands, there has been no indication that the needs of people and businesses in Northern Ireland are a priority, and that needs to change."