A committee of MPs has questioned whether there will be enough time to make the necessary arrangements to avoid large-scale disruption if Britain leaves the EU without a deal.
The Commons European Scrutiny Committee warned that a no-deal Brexit and an abrupt departure from the single market and customs union on March 29 next year “remains a distinct possibility”.
And it warned that such an outcome would be “extremely disruptive for many sectors of the economy”.
The government has said it hopes to conclude a withdrawal agreement with the EU in the autumn, in order to provide time for it to be ratified by the European and Westminster parliaments before Brexit day.
But last week’s European Council summit passed without a breakthrough, and there has so far been no announcement of a mooted special Brexit summit in November.
The government has begun formal preparations for a no-deal Brexit, publishing more than 100 technical guidance documents covering many possible impacts.
Despite this activity, the committee’s report said there remained “considerable uncertainty” about the practical implications of no deal for UK trade links with the EU and the rest of the world, transport connections and the status of the Irish border.
Many of the potential disruptive effects are “not within the gift of either the UK or EU to unilaterally mitigate”, the report warned.
While Theresa May has said EU nationals’ status in the UK will be protected after a no-deal Brexit, it would be a matter for each individual EU state whether to do the same, the MPs said.
And the UK cannot require the EU to reciprocate if Britain took steps to allow food and medicines in without new controls.
It was “unclear” what restrictions on trade with and transport to the UK might be applied by the EU.
“While we agree that it would be in both sides’ interest to avoid the worst disruption in the event of an exit without a withdrawal agreement, we note that the Exiting the EU Committee has questioned the government’s approach of expecting there to be sufficient time and political goodwill to negotiate bilateral contingency measures,” said the Scrutiny Committee report.
“We are inclined to agree, especially as the talks would take place in the context of a failure to agree a comprehensive withdrawal agreement on issues the EU had identified as key to an orderly withdrawal.”
The EU’s chief Brexit negotiator Michel Barnier has explicitly ruled out “mini-deals” in the case of a failure to reach an overall agreement, the report noted.
“The lack of clarity about the immediate impact of a disorderly UK withdrawal is particularly problematic in relation to the border between Northern Ireland and Ireland,” said the report, suggesting that a no-deal Brexit will make a customs and regulatory border “necessary”.