British immigration officials have warned migrants in northern France they are being lied to by people smugglers promising them a better life in the UK.

Their intervention comes at a time when the number of migrant crossings has been increasing, partly because of camps being cleared.

There was another clearance on Tuesday, when almost a thousand migrants were removed from a gym in a Dunkirk suburb.

Invited by the French authorities, the British officials' work in France includes "countering the misinformation being spread by other sources, including organised crime groups", the Home Office said.

Migrants are being warned that people smugglers are not telling the truth about the journey, or about what awaits them if they make it to Britain.

The Home Office said it was determined to stop "this reckless and illegal activity by stopping boats from leaving French shores".

Those removed from a gym in the Dunkirk suburb of Grande Synthe included several families with young children, the charity Care4Calais said.

Another charity, Help Refugees, said about 250 children were there, 150 of who were unaccompanied.

"These evictions are about political bravado rather than humanitarian concerns," said Maddy Allen, the charity's field manager for the area.

More than 200 police officers escorted aid workers from the site early on Tuesday, before coaches arrived and migrants were escorted on to them.

They are being taken to temporary shelters and will be allowed to apply for asylum.

According to French police, the evacuation followed concerns over security and hygiene.

But Care4Calais said it had been pointless because many of those evicted would soon be back in Dunkirk and Calais in their quest to reach the UK.

"Continual forced evictions don't affect the underlying issues that cause people to risk their lives crossing the Channel," said founder Clare Moseley.

"The men, women and children that we talk to every day do not want to take these risks; all they want is for their asylum claims to be heard."

Immigration minister Seema Kennedy said: "People thinking about making the perilous journey across the English Channel in a small boat are taking a huge risk with their lives and the lives of their children."

Meanwhile, 29 arrests have been made as part of an investigation into a large migrant smuggling network, Europol said.

Last week, the National Crime Agency arrested six British men suspected of smuggling migrants.

Elsewhere, the Ocean Viking aid ship has picked up 61 people from a plastic boat off the coast of Libya.

At least two people have died and 14 are missing after a boat filled with migrants hoping to reach Europe capsized off the coast of Tunisia.

And Malta has refused to accept 90 migrants rescued by an Italian Coast Guard vessel.

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UK officials tell migrants in France: You are being lied to by people smugglers - Sky News