The Ministry of Defence has confirmed 320 members of the armed forces have been brought in to get hauliers out of Kent.
The army has been drafted in at several testing sites across the country with 1,400 currently supporting the response to the pandemic.
Despite the travel ban being lifted nearly two days ago, it's been challenging to get the backlog cleared.
Ferry company DFDS has only been able to take 144 lorries home since the border reopened despite having capacity for 4,000.
At least 6,000 HGVs were stranded in Kent yesterday and while some have since left hundreds of drivers face days at Manston Airport with 2,300 tested for Covid-19 so far.
Transport Secretary Grant Shapps says more than 2,300 drivers waiting to leave have tested negative, while three were positive.
Now DFDS says logistical issues have hampered efforts to repatriate stranded truckers - and it's calling for staff to work on Christmas Day after the traditional port closure was lifted.
This morning lorries were seen heading towards the Port of Dover but roads remain gridlocked. It's expected clearing the HGVs, which at one point numbered at least 6,000, will take days.
And now Transport Secretary Grant Shapps says the border will stay open tomorrow and across the festive period.
He tweeted: "As testing in Kent continues (latest figures & outcomes soon) I've spoken to my French counterpart @Djebbari_JB & we've agreed the UK/French border at Eurotunnel, Dover & Calais WILL remain open throughout Xmas in order to help hauliers & citizens return home as soon as possible."
The French Ambassador to the UK Catherine Colonna tweeted this morning to say 26 firefighters had headed to Dover to deliver 10,000 tests.
At Manston Airport, where thousands of lorry drivers are getting tested before heading home, drivers told our reporter they expected to be stuck for another two days.
They think around 1,000 have been tested and food is being passed to them over the fence. But they claim while toilets are available there are no shower facilities.
One big issue is lorry drivers parked on the roads who can't get in have no food or facilities.
Attela Kaliman and Robert Henstencz speak about life at Manston
In Ashford, residents responded to a plea on Facebook from a German driver who desperately wanted a shower by organising for truckers to use a nearby Holiday Inn.
Despite a huge military-coordinated testing scheme starting in Manston and Dover, the number of lorries continued to grow yesterday forcing highways bosses to use the London bound carriageway of the M20 for more parking.
The motorway is shut in both direction to allow for Operation Stack - essentially a holding pen - between 8 (for Leeds Castle and 9 for Ashford) and all the way from 7 (for Maidstone) to 13 (for Folkestone) on the coast bound section.
This is in addition to the 4,000 capacity (revised down to 3,800 to allow for testing) at Manston.
It is thought there were more than 6,000 lorries parked up in Kent yesterday.
Yesterday morning scuffles broke out at Dover between police and frustrated drivers who, having been stranded at the port for days, were seeing other lorries coming from Manston and entering.
Those in Dover were being tested in their vehicles from about 4pm in an attempt to clear the gridlock - although drivers are still being told to head to Manston, with others being diverted to a centre on Sheppey.
The first few cars and lorries were seen heading for a ferry after receiving a negative Covid test at around 6pm. There were reports this seemed to stop at around 9pm and tension starting to flare again.
There were also stand offs at Manston as drivers attempted to leave and others enter. Later in the day an army of people arrived to get food and drink to the drivers.
Graham Pask from the Road Haulage Association called the situation a "humanitarian crisis" and compared the French government to a "dictatorship" "holding lorry drivers hostage".
Talks between the French and the UK governments came to an end on Tuesday evening and the ban was lifted that night.
All drivers, irrespective of nationality, require a lateral flow test. This can detect the new strain of Covid-19 and provide results in around 30 minutes, rather than the 24 hours required after a PCR test.
The French government will also carry out sample testing on incoming freight to the UK.
Communities secretary Robert Jenrick confirmed it would take "a couple of days" to clear the backlog and drivers should still avoid heading to Kent.
If drivers test positive they must isolate in hotels, the initial cost of which will be picked up by the government.
Transport Secretary Grant Shapps said after the deal was made with the French: "I am pleased that we have made this important progress with our French counterparts this evening. This protocol will see the French border reopen to those travelling for urgent reasons, provided they have a certified negative Covid test.
"We continue to urge hauliers not to travel to Kent until further notice as we work to alleviate congestion."
Rules for drivers will be temporarily relaxed to allow them to get through quickly.
The Road Haulier Association said drivers in Thanet had a 'miserable existence' as facilities were not in place to help them.