Farmers must stop sending their animals on "cruel and unnecessary" long-distance journeys across Europe, campaigners said today, as figures showed a big increase in the number of sheep and calves being exported alive during 2010.

Launching an advertising campaign against live animal exports for the welfare organisation Compassion in World Farming, the actor Joanna Lumley called for a maximum journey time of eight hours to be imposed and enforced across Europe. "We don't have to illustrate how simply ghastly this trade is," she said, sitting on board a Routemaster bus in Trafalgar Square. Last year's resurgence was a sign that "our eye has been taken off the ball", she said, but added: "This year, 2012, is the year of powerful change … we can do it. We can make it happen."

Although the live export trade has shrunk dramatically since the 1990s, last year saw "a significant increase", according to CIWF. It estimates that nearly 80,000 live sheep and calves were exported, compared with around 25,400 in 2010. Pigs and goats have also been loaded onto transporters, taking the overall total for last year to around 80,600.

While pushing for an end to the trade, animal welfare groups such as CIWF regard a bid to impose an eight-hour maximum on all EU journeys as a good compromise. A petition launched by Dan Jørgensen, a Danish MEP, due to be closed today, has attracted more than a million signatures.

"Eight hours is a long time," acknowledged CIWF chief executive Philip Lymbery. "Nevertheless we know some of Britain's animals over the last year have gone as far as Spain on journeys of up to two days, so eight hours would be a huge step forward."

The National Farmers Union says that transporting live animals from one part of Europe to another is "legitimate and lawful", provided the animals are well cared for during the journey. Peter Garbutt, the NFU's chief lifestock adviser, said that journeys of more than eight hours made up "a very small but important minority" of all movements. "We believe the current regulations are based on sound science and when enforced do not compromise animal welfare," he added.

But animal welfare groups argue that this is simply not possible, claiming that investigations into long-distance live exports have shown some animals being kept in cramped conditions with no access to water.

They say that during the journeys, which can often last for days, the animals can collapse onto the floor of the truck, where they risk being trampled. Animals suffer terribly during transit, they say, with some becoming ill and, in the worst cases, dying.

Responding to the NFU's position, Lymbery said: "It is far too easy for us to find cases of animals suffering in the live export trade, and common sense tells you that taking a couple of tiny calves to Spain isn't going to do them any good."

In Ramsgate, from where, according to Defra, all UK live exports have left as of May last year, opposition has been building for months. Ian Driver, a local councillor, has launched an e-petition denouncing the exports as "unnecessary" and calling for a change in the law to allow port owners to refuse trade on ethical grounds.

CIWF and Lumley said the cost of shipping from Ramsgate should be increased in order to deter exports. According to its figures, which were obtained from Defra, 223 truckloads of live animals were taken through Kent ports in 2011 – 80,664 in total. According to Eurostat, 25,417 sheep and calves were exported in 2010. "Let's make people pay the cost of farming," said Lumley.

A spokesman for Defra said: "Ideally we'd rather see the export of meat than live animals. But where animals are transported we want good welfare standards, which includes ensuring they have suitable food and water and that journey times aren't too long. We are pushing in Europe for a maximum journey time or a maximum distance limit to stop slaughter animals going on unnecessarily long journeys and want vulnerable animals, such as unweaned calves, to get greater protection."