MPs have said a return of border checks between the Republic of Ireland and the north seems "inevitable" after Britain leaves the European Union.
The Exiting the EU Committee in the House of Commons said it appeared impossible to marry the decision to pull out of the single market and customs union with the intention to create a “frictionless” border.
The committee said the proposals to deal with the issue, like the use of technology to create a “light touch” border, were speculative and untested.
The report has split the group, with a number of Tory MPs present rejecting the assessment.
The research conducted by the committee echoes concerns raised by the Irish government in relation to the border.
The Irish Taoiseach, Leo Varadkar, has said without an assurance on the border issue, EU leaders will not allow the Brexit talks to proceed to the next stage.