The home office has been accused of "retreating to a fortress Britain" in its drive to create secure electronic borders.
DUP MP Sammy Wilson says the result will be that "the people of Northern Ireland will be treated worse than foreigners", with more onerous identity requirements made of them than of people travelling to Britain from the Republic or France.
Mr Wilson raised the temperature in the growing "e-borders" debate following private discussions between the DUP and home office minister Tony McNulty and written parliamentary answers from immigration minister Liam Byrne to the Conservative Northern Ireland spokesman Owen Paterson.
Mr Paterson had asked what the implications were of an e- border system "circumscribing Great Britain for travel between mainland Britain and Northern Ireland" and, specifically, what documents will be required under the proposed scheme for travel between Britain and Northern Ireland.
Mr Byrne replied by way of reference to section 14 of the Police and Justice Act 2006, which introduced a new power that will allow police to collate passenger, crew and service information on air and sea journeys within the United Kingdom.
The specific police requirements under this power are still under discussion and final proposals will be subject to a 12-week consultation. However, the minister told Mr Paterson: "It is expected that this police power will only apply to air and sea routes between Great Britain and Northern Ireland.
"Passengers will not be required to use passports, but may be required to produce one of several types of documentation, including passports, when travelling, to enable the carrier to meet the requirements of a police request."
This seems to confirm unionist fears that British citizens from Northern Ireland will be uniquely required to provide forms of identification when travelling to other parts of the United Kingdom.
In a furious statement last night, Mr Wilson said the emerging detail rendered prime minister Gordon Brown's recent assurances to DUP leader Ian Paisley "meaningless . . . or indeed even worse".
As reported in The Irish Timeslast week, Mr Brown told Dr Paisley that citizens travelling between Northern Ireland and Britain would not be subject to passport controls. Dr Paisley interpreted the prime minister's assurance as meaning British citizens in the North would be treated on the same basis as their fellow citizens in the rest of the UK.
However, Mr Wilson maintained: "If these proposals go forward people in Northern Ireland, who are citizens of the United Kingdom, will have restrictions placed on their travel to Great Britain yet, shockingly, this scheme will not be applied to those coming into Great Britain from the Republic of Ireland or France. If this plan goes ahead, the people of Northern Ireland will be treated worse than foreigners."
The East Antrim MP said it was clear the new restrictions under the Police Act would require people using an airline or ferry company to provide written answers about where they were going, where and with whom they were staying.
This, said Mr Wilson, would "hamper last-minute travel by ticket users", such as those travelling to football matches or making quick travel plans to deal with family emergencies or deaths. "This appalling plan will take away one of their fundamental rights, namely freedom to travel in their own country," declared Mr Wilson.
Lord Trimble, a former Ulster Unionist leader and now a Conservative peer, also reacted angrily, saying: "Rather than reaching out to embrace the whole Common Travel Area [ between the UK and Ireland], the Home Office are retreating to a fortress Britain."