Contractors initially said the huge £104 million project on the M20 would open to traffic this month, but delays to the scheme have pushed it back.
There are fears the hold-up could spell disaster for the surrounding road system after plans were revealed for a temporary HM Revenue and Customs (HMRC) station at the Waterbrook truckstop in Sevington, which sits just off the A2070 not far from the current junction 10.
The government wants to use the site as a checkpoint to allow lorry drivers with incorrect paperwork to pick up permits for onwards travel following Brexit, but there are concerns it will only add to disruption if junction 10a is not open.
Highways England says it plans to partly open the junction to allow lorries heading to the truckstop to use it, but that not all traffic will be able to access the roundabout.
Project manager Tom Selby revealed the delay at a meeting of the joint transportation board (JTB) at Ashford Borough Council last Tuesday.
“Being open for traffic on October 31 won’t be do-able,” he said.
M20 junction 10a work will 'transform' the motorway
“We’ve had some delays which wouldn’t be appropriate to go into in this meeting.
“Trucks will be able to come from the coast and London-bound and use the new link roads to the truckstop but that’ll be under certain conditions.
“I know that’s not quite what you wanted to hear but that’s where we are at the moment.”
Ashford MP Damian Green met with the Treasury minister and officials from HMRC on Tuesday to discuss the situation.
He said: “I was very cocerned to learn that the Ashford site will be used for in-bound lorries that come across the Dover straits and will be used as a turn-around site for those that arrive and might need new papers.
“It is difficult to see how - if it is not opened - junction 10a will be able to cope.”
Mr Green says he and other MPs now want an urgent meeting with Michael Gove, the cabinet minister in charge of Brexit, about the implications for the town.
He said HMRC was unable to say how many lorries it expected would need additional paperwork.
Individual checks on lorries might take one to two hours for each vehicle.
“It was not reassuring,” Mr Green added.
“My main point is we will have a lot of extra lorries and, with the existing traffic arrangements, run a real risk of disruption and delays to the town.”
Ashford Borough Council deputy leader Paul Bartlett (Con) is disappointed the opening of the junction has been pushed back.
“It is essential it opens fully,” he said.
“We will be on the frontline in Ashford next month and it seems most unfair that we will be left to pick up the pieces.
“All parties - ABC, Kent County Council and Highways England - will have to work very hard between now and October 31.
“If we put in all of the work between now and then, I think we will be OK, but if not the situation could be chaotic.
“The pressure is now on - all of the parties have really got to pull together and get this sorted out.”
A Highways England spokesman said work is progressing.
“We have made huge progress in delivering a new junction on the M20 near Ashford, which will tackle congestion and bring huge benefits for the town,” he said.
“The scheme is now in its final stages and we are doing everything we can to ensure we can meet our commitment of having the new junction open to traffic this autumn.”