By Anna Pujol-Mazzini

LONDON, Feb 22 (Thomson Reuters Foundation) - Young refugees who came to Britain alone as children and were "traded like cattle" by smugglers have urged the government to ensure safe, legal routes to the UK after it announced plans to scrap a scheme to take in vulnerable child migrants from Europe.

The open letter signed by 17 refugees, aged between 16 and 22, adds to growing calls from charities and celebrities to keep the scheme open.

Under the so-called Dubs amendment passed by parliament last year, Britain agreed to accept vulnerable refugee children who arrived in the European Union before March 20, 2016.

But earlier this month, the government announced plans to drop the scheme it said encouraged human trafficking.

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"Many of us have been traded like cattle between groups of smugglers on our journeys," the refugees, from countries such as Syria, Afghanistan and Eritrea, wrote.

"Many of us boarded over-filled rubber boats to get here. Many of us know someone who died on the journey," the letter published on Wednesday said.

"We are the lucky ones – the ones that got here safely."

One of the refugees, who chose to remain anonymous, spent eight hours in a freezer during his journey, according to the British Red Cross which has been helping the group.

An 18-year-old from Iran, who came to Britain in a truck from the French port town of Calais, said he decided to sign the letter after witnessing deaths and abuse on his journey.

"Assaulting women, sexually abusing children, the smugglers are really not nice people," he said. "I saw so many people die, this is a deadly journey."

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The letter was published on the same day experts from refugee and children's charities were due to give evidence to a parliamentary committee on the impact of the government's plans in an emergency session.

Last week more than 200 actors, musicians, authors and broadcasters - including actress Keira Knightley and rock band Coldplay - said the government's decision to end the scheme was shameful and embarrassing, and urged it to reconsider.

The decision has also been criticized by aid agencies, opposition lawmakers, celebrities and the Archbishop of Canterbury.

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Two petitions calling for the government to save the scheme have received more than 50,000 signatures.

One petition was brought by the politician who sponsored the Dubs scheme, Alf Dubs, a Jewish refugee who came to Britain as a child fleeing Nazi persecution. The other was started by volunteers working with migrants in Calais.

Conflicts and poverty in the Middle East and Africa have forced more than 1 million people to head to Europe, fueling the region's largest migrant crisis since World War Two.

Around 30,000 unaccompanied children arrived in Greece and Italy alone in 2016, according to the United Nations children agency UNICEF.

(Reporting by Anna Pujol-Mazzini @annapmzn, Editing by Katie Nguyen. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters that covers humanitarian news, women's rights, trafficking, property rights, climate change and resilience. Visit http://www.news.trust.org)