Motorists heading for Dover spent the night in their cars after police warned that delays could last until Monday.
British officials are being drafted in to work with French border police after the Government admitted motorists had suffered "extraordinary disruption" at the port.
People travelling, many heading off for a summer break, spent up to 15 hours in standstill in queued traffic while water supplies were dropped along the jam by police helicopter.
A Sikh humanitarian relief organisation also pitched in with the effort, delivering nearly 6,000 bottles of water along with snacks to the stranded motorists.
Kent Police said the disruption was down to a "vast volume of holiday traffic" coupled with delays caused by heightened security at the border in the wake of terror attacks.
The Home Office said it would send in the UK Border Force to help French authorities at the Port of Dover.
Increased checks were put in place by French authorities at the port in light of recent terror attacks, but questions have been raised about staffing levels to deal with the huge increase in people travelling at this time.
Port authorities said French border control booths at Dover had been "seriously understaffed overnight", claiming coaches were at one point having to wait 40 minutes each for all passengers to be checked in as only one French officer was available.
A spokesman said concerns about staffing levels were raised with the British government earlier in the week, and said those had been passed to French authorities.
The Government said as well as increased help with border checks, Kent police will be "proactively managing" traffic to get drivers through more quickly.
A Government spokeswoman said: "We recognise the security pressures that French law enforcement organisations are under at Dover and we have agreed the UK Border Force will assist the PAF (French border police) with border checks to remove the backlog.
"We understand that there has been extraordinary disruption in the Dover area today but safety is paramount.
"Measures are also being taken on the approach to the port where Kent Police will be proactively managing traffic to speed up the process."