The government is warning of worsening chaos at Britain's ports as lorry traffic returns to normal levels.
But Brussels says it won't grease the wheels unless Boris Johnson abandons his plans for a 'Singapore on the Thames.'
Projections from the Cabinet Office anticipate cross-Channel freight will rise rapidly following a New Year slowdown, The Times reported.
Tailbacks stretching for miles are expected if drivers aren't equipped with the correct customs paperwork or negative covid tests which the French demand.
Lorries queue in at the border control of the Port of Dover on Friday. Traders stockpiled goods on both sides of the Channel before Jan. 1 but now supplies are dwindling, around 2,000 per day were crossing in the week to Jan. 10 - the normal level is 6,000 - and it will quickly rise back to that figure in the coming days
Brussels is turning the screw on Boris Johnson to abandon plans for a 'Singapore on the Thames' (pictured: the Prime Minister leaves Downing Street on Wednesday, left; and European Commission President Ursula von der Leyen speaking at a conference yesterday)
'Of course we can in future discuss how to have less friction,' an EU diplomat told The Times.
'Discussing further facilitation or ways to reduce friction would depend on what the UK is doing and where they want to go.
'Initiating that conversation and negotiation will not be made easier if the other side of the table is talking up deregulation or Singapore on the Thames.'
Britain formally left the EU last January but remained within its regulatory orbit until the end of the year under the terms of its divorce.
Although the two sides struck a Christmas Eve free-trade deal, avoiding trade tariffs and quotas, the departure from the single market and customs union has resulted in bureaucracy and hold-ups.
Britain and the EU are continuing to tie up loose ends to allow for free flowing freight while the Cabinet Office has warned of the worst days at the ports since December 31.
Lorry traffic lulled after Brexit as stockpiles on either side of the Channel had been prepared by nervous traders.
But now those supplies are dwindling and traffic is picking up again.
Stephen Bartlett, chairman of the Association of Freight Software Suppliers, told The Times: 'We've been lucky so far. Traffic volumes through ports have been quite low. But the next couple of weeks are going to be the main test.
'There could be more disruption as trucks come through that aren't prepared with paperwork or drivers who haven't been tested for Covid. There will be more issues. Then we could see some of these lorry parks starting to fill up.'
The Road Haulage Association estimates that of the 2,000 outbound lorries a day through Dover and the Channel Tunnel in the week ending Jan. 10, 20 per cent were turned back.
It said problems will surge as these numbers increase to the normal 6,000 a day.
Around half of the turn-backs are down to post-Brexit paperwork and another half are because drivers don't have the negative test demanded by the French.
The port at Dover on Tuesday as hauliers face post-Brexit customs rules and covid testing
A sign at the Port of Dover ferry terminal warns lorry drivers to have their Covid-19 tests ready for inspection on Tuesday
Britain's ports were already under huge pressure before January 1 after covid shattered the system for shipping goods around the world and children lost out on their Christmas presents.
Last Friday, tailbacks for more than mile had built up outside a customs facility in Ashford, Kent, with many forced to wait for days.
Last month the French banned HGV drivers from crossing the Channel in a desperate bid to prevent the spread of 'mutant' coronavirus detected in London and the southeast.
The ban left thousands of lorry drivers stranded in Kent during the Christmas period and led to clashes with police at the border.
This was only resolved when the UK gave drivers lateral flow tests which take 20 minutes to produce a positive or negative result.
Since then the French have quibbled over the accuracy of the tests and called on the Britain to introduce a fully saliva-based PCR test for the truckers.
Ministers, who are already drawing up plans to allow supermarket lorries to bypass queues at the Channel ports amid fears of food shortages in the UK, are concerned that the demand will result in gridlock at the border again.