The leader of Portsmouth City Council says he can not allow government inaction to "crucify Portsmouth" in the event of a no-deal Brexit.
Gerald Vernon-Jackson said the auhtority and Hampshire County Council had already spent £4m on preparations to avoid gridlock near the city's port.
The government has just announced port towns in England will receive an extra £9m to pay for preparations.
But Mr Vernon-Jackson said the money was "too little, too late".
Speaking on Radio 4's Today programme, the Lib Dem council leader said the government had so far refunded £350,000 of the £4m and it was unclear how the £9m would be allocated.
"We've had to plan so the whole of the south coast on the M27 doesn't grind to a halt," he said.
"The check-in gate for the lorries is really close to the motorway - 14 lorry lengths away.
"For the first time in 40 years, every lorry will have to have pre-customs clearance.
"Even if it is just two minutes extra for their check-in period, the government is saying we are likely to have 60 lorries queuing on to the motorway."
About 500 lorries a day pass through Portsmouth Port but that number is expected to rise to 2,000 as hauliers try to avoid Dover, which handles about 10,000 lorries a day.
Mr Vernon-Jackson said triage points and lorry parks had been created so drivers without the right documents could download and print what they needed.
He said: "We can't allow government inaction and inefficiency to crucify Portsmouth."
Earlier, Michael Gove, minister in charge of no-deal planning, said: "We're doing everything that we can in order to make sure that traffic continues to flow.
"I can't guarantee that there will be no delays but we're seeking to ensure that we minimise the prospect of delays so that, whatever bumps in the road we face, we're able to ride them out."