The government's handling of a new border with the EU was "largely successful" but relied on temporary measures that are "not sustainable", the National Audit Office (NAO) has said.
The NAO praised it as a “significant achievement”, noting that essential elements had been delivered and there had been no large queues at the border.
However, more controls are due to be phased in over the first half of 2022 and the report added that the current model controls “cannot go on indefinitely”.
On the Northern Ireland Protocol, the NAO said the situation was “inherently challenging” and urged the government to implement any deal reached with the EU on changing the protocol “quickly”.
Gareth Davies, the head of the NAO, said: “We recognise the significant achievement of government, departments and third parties in delivering the initial operating capability needed at the border for the end of the transition period.
“However, this was done in part by using interim measures and by delaying the introduction of full import controls.
“Much more work is needed to put in place a model for the border that reduces the risk of non-compliance with international trading rules, does not require any temporary fixes, and is less complicated and burdensome for border users.”
The NAO report said burdens on businesses would increase as new controls were introduced, many of which would become evident in the wider supply chain rather than at the border itself.
Trade with the EU has recovered slightly after falling 44% in the first quarter of 2021 but remains 13% below the level of the last three months of 2020.
The report said it was not possible to disentangle the impact of Brexit from the impact of the pandemic, but “reductions in the UK’s trade with the EU are significantly greater than the UK’s trade with the rest of the world over the same period”.
The report also noted UK exporters were at a disadvantage compared with EU exporters, as the EU had implemented the full set of border controls while the UK was not scheduled to do so until July 2022.
Despite the delay, the government’s Border and Protocol Delivery Group still believes there is a high risk that traders and hauliers will not be ready for the introduction of more controls in January 2022.
Dame Meg Hillier, chair of the House of Commons Public Accounts Committee, said: “Today’s report finds that the government was able to do enough to avoid the much-feared queues at the border once the UK-EU transition period came to end.
“The delayed rollout of full import controls means it’s still not a level playing field for some UK businesses.
“Leaving the EU has meant businesses have had to grapple with more paperwork and additional cost. Government must help businesses adapt to the new rules and put in place border controls that work for all.”