Emergency powers to handle post-Brexit queues of lorries heading for France are being made permanent, signalling the government expects further cross-Channel disruption.

Operation Brock, a traffic management system designed to cope with queues of up to 13,000 lorries heading for mainland Europe across Kent, was meant to end by October 2021, after being extended once when the Brexit transition period ended in December 2020.

But ministers are planning to make the provisions indefinite by removing “sunset clauses” from the legislation that set out when the powers would expire, the Guardian has learned.

It means the emergency protocol can be activated at any time to govern the flow of lorries around the Port of Dover and Channel Tunnel at Folkestone with contraflow systems.

The change was published quietly in a consultation response on the government’s website during parliamentary recess while MPs were away from Westminster, with statutory instruments to be laid in September.

Grant Shapps, the transport secretary, has previously acknowledged that the traffic system, which allows lorries exclusive use of one side of the M20 motorway, “frustrated residents and businesses”.

The measures were enacted in October 2019 in relation to Brexit and in December 2020 after the French border closed as a result of coronavirus concerns, as well as briefly again this summer in anticipation of heavy holiday and haulage traffic to France.

Under the contingency plan, part of the eastbound M20 – the main artery to Dover and the Eurotunnel at nearby Folkestone – is closed to normal traffic and made available exclusively for lorries. Other vehicles instead use the London-bound side of the M20 in a contraflow system.

The government’s consultation response said removing the sunset clauses would provide the Kent Resilience Forum with “the ability to respond to circumstances appropriately and swiftly, minimising any disruption”.

“The Operation Brock response plans will continue to be for temporary use and only implemented if strictly necessary to minimise traffic congestion in Kent caused by disruption at the Short Straits,” it said.

It highlighted possible uses as a “contingency traffic management measure for disruption, caused by, for example, bad weather or industrial action” in future.

However, MPs said the underlying cause of the threat of cross-Channel disruption was Brexit. Sarah Olney, transport spokeswoman for the Lib Dems, said: “It’s British businesses and consumers who are being harmed the most by the Conservatives’ botched deal with the EU.

“With this move, they’re essentially admitting that the disruption that local residents have had to endure will be long-lasting and persist for the foreseeable future. Instead of fixing the underlying cause and listening to the concerns of the people of Kent, all Tory ministers are doing is papering over the cracks. It’s not good enough.”

Naomi Smith, the chief executive of the internationalist campaign group Best for Britain, said: “This is an admission that far from ‘teething problems’, the government expects supply problems from their rushed Brexit deal to continue indefinitely.

“Shelves are empty and our supply chains are already at breaking point. The government should be seeking improvements to their deal with Europe rather than preparing to make Kent a permanent lorry park.”

The government has previously said the flow of cross-Channel freight since Brexit has been better than anticipated, with only “2-3%” of trucks turned away for not having the paperwork or Covid tests required, and no expectation that the worst-case scenario it had modelled of 7,000 trucks queuing in Kent would be realised.

Operation Brock has proved unpopular with residents as a way of managing lorry traffic, but the authorities believe it has reduced disruption overall. The Department for Transport has been contacted for comment.