A huge operation in Dover has been uncovered after an investigation by Dogs Trust revealed puppies are being smuggled in to the country.

The animals, most of which are underage with umbilical cords still attached, are sedated before they get to the English border so they do not make a noise.

It is thought 82% of the pups intercepted at the border are popular breeds such as pugs and French bulldogs.

Scroll down for audio and video

A litter of underage puppies smuggled into the UK from Eastern Europe were discovered with their umbilical cords still attached following a 30-hour journey.

The five pint-sized English Bulldog puppies were just four weeks old when they were seized by officials at Dover - 11 weeks below the legal age for transportation.

Their umbilical cords were attached and their microchips had been taped to their carriers with the transporters bringing their own surgical tools to insert the chips.

The operation also found documents are being falsified to make the animals appear older than they actually are to keep suspicion at a minimum if breeders are stopped by border officials.

Veterinary director at the charity Paula Boyden said: "These shocking cases clearly show that urgent action is needed to stop the puppy smuggling scandal.

"The number of prosecutions is far too low and the lack of visual checks at ferry ports and borders is unacceptable.

"We want to see stronger deterrents including prison sentences for those caught trafficking puppies."

Ms Boyden is calling on the government to look again at laws for travelling pets once Brexit negotiations get fully underway.

She added: "The government must revise pet travel legislation when the UK leaves the EU and ensure that puppies entering this country are healthy, not underage and are not being brought in to sell on to unsuspecting buyers via a scheme meant for non-commercial use."

Undercover footage released by the charity shows a vet in Lithuania selling sedatives so that puppies, some as young as four weeks old, can be taken across the border.

In another case canines were seen vomiting and eating their own faeces during a journey in a packed van from Lithuania.

It comes as Kent has been listed as the fourth largest area in the country for puppy farms.

In 2016 168 (4.6%) of all calls received by the RSPCA related to puppies being traded.

The research also found ads are being posted on Gumtree.