Measures to avoid a hard border in Ireland could be ready within three years, according to an independent commission chaired by senior Tories.
The group's recommendations are aimed at using existing legal frameworks and technology to find alternatives to the controversial backstop measure in Theresa May's Brexit deal.
But critics said the proposals would be costly and would come too late for a deal to be reached by the current October 31 Brexit date.
The Alternative Arrangements Commission was set up by the Prosperity UK think tank.
Its interim report recommends:
- Investigating the possibility of creating special economic zones to cover the border.
- Creating a multi-tier trusted trader programme for large and medium-sized companies, with exemptions for the smallest firms.
- Using mobile units to carry out sanitary and phytosanitary (SPS) checks - covering food safety and plant and animal health - away from the border.
- Drafting an alternative arrangements protocol which could be inserted into either the Withdrawal Agreement or used in any other Brexit outcome.
The commission was chaired by Tory former ministers Nicky Morgan and Greg Hands.
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Treasury Select Committee chairwoman Mrs Morgan said: "The commission has met its three conditions: to uphold the vital Belfast-Good Friday Agreement; to harness existing technologies and customs best practice, not any futuristic high-tech unicorns; and to be compatible with any of the possible Brexit outcomes, including the existing Withdrawal Agreement.
"A successful agreement and roll-out of alternative arrangements would supersede the need for the backstop."
But Owen Smith, former shadow secretary of state and a supporter of the People's Vote campaign for a second referendum, said: "The idea of trying to replace the Northern Ireland backstop with so-called alternative arrangements has already been tested to destruction.
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"There is no political will to do so from either Ireland, the rest of the EU or most importantly the people of Northern Ireland, particularly those living on or near the border."
He said the commission was "a desperate attempt to make a square peg fit into a round hole in order to try and hold the warring factions of the Conservative Party together".
Naomi Smith, head of the pro-EU Best for Britain campaign, said "a solution years down the line won't cut it: we have a deadline of October 31 this year" and the proposals would "wrap the island of Ireland in red tape and bureaucracy - at a hefty cost to the British taxpayer".
"A quicker, cheaper and more efficient option would be to stop Brexit," she said.
