The world's largest toymaker Lego caved in to pressure Thursday from a hugely successful Greenpeace campaign targeting a deal with oil giant Shell and linking the iconic plastic bricks to catastrophic Arctic oil spills.

Announcing the decision to end a multi-million-dollar marketing tie-up with the oil company, Lego chief executive Joergen Vig Knudstorp said the Danish toy company did "not want to be part of Greenpeace's campaign".

Since July nearly six million people have viewed a Greenpeace video on YouTube entitled "Everything is NOT Awesome", a wordplay on a Lego film -- featuring an Arctic Lego landscape dotted with oil rigs, polar bears and children playing -- until they are all drowned in oil.

The only thing left standing is a Shell flag and the slogan, "Shell is polluting our kids' imagination".

- Children 'our major concern' -

The campaign targeted a 2011 deal -- worth an estimated 103 million dollars (81 million euros) according to Danish media reports -- to sell special Lego models of Ferrari cars at Shell petrol stations around the world.

Since it began, more than a million YouTube viewers have mailed protests to the toy company via a Greenpeace website.

"It's a victory of the people," Annika Jacobson at Greenpeace Nordic told AFP.

"We would not have achieved this without all the people that have signed our petition and asked Lego to stop the partnership."

She said the decision marked a major turnaround for the toy company which initially claimed it had nothing to do with the environmental group's fight to stop Shell prospecting in the Arctic.

On Thursday Lego's chief executive defended the company's partnership with Shell and criticised the Greenpeace campaign for using "the Lego brand to target Shell".

"A co-promotion like the one with Shell is one of many ways we are able to bring Lego bricks into the hands of more children and deliver on our promise of creative play," Knudstorp said in a statement published in Danish daily Politiken, where he announced that the Shell deal will end when the current contract expires.

"Children are our major concern and the central focus of our company... The Lego brand, and everyone who enjoys creative play, should never have become part of Greenpeace's dispute with Shell."

- 'Signal to oil companies' -

Greenpeace accused Shell and other oil companies of using wholesome brands to boost their image.

"With Lego they had a very good and popular brand, associated with sustainability, targeting kids... very innocent," she added.

Lego's climb-down was a sharp reminder to other multinationals of the speed of social media campaigns and the need to react quickly to scandals, according to PR experts.

"Lego's apology to clients was a dramatic one," Morten Holm at Copenhagen-based PR firm Holm Kommunikation told AFP.

"Greenpeace's campaigns have been fortified with great use of YouTube, Facebook... it goes very fast. And the more time passes, the greater the excuse and the more the embarrassment."

In August, Shell submitted a new plan for drilling in the Arctic, off the coast of Alaska -- upping the intensity of the Greenpeace Lego-Shell campaign.

Shell halted its Arctic programme in 2013, following several embarrassing mishaps with drilling rigs and high-profile clashes with Greenpeace activists.

And Lego's announcement will make it even harder for the company to avoid negative publicity in the future, said Jacobson.

"The same thing that happened to the tobacco industry is now happening to oil companies... They are totally dependent on not being pictured as 'bad' companies," she said.

"But this sends an important signal to oil companies that they will not be able to use other brands to gain social acceptance."

A spokesman for Lego would not confirm the value of the co-promotion partnership.

He also declined to say when the contract with Shell would end but Greenpeace Nordic believed it would be within 18 months.