Work on building a wall along the approach road to the French port of Calais to try to stop migrants from jumping aboard trucks bound for the U.K. will begin this month, British officials said.

British Home Office Minister Robert Goodwill said the kilometre-long, four-metre-high wall is part of a $29-million package of security measures agreed to by Britain and France in March.

"We've done the fence and now we're doing the wall," Goodwill said on Tuesday.

Shrubbery has already been cleared on one side of the Rocade road but there was no sign of workers or machinery at the site on Wednesday. A local official said the project would be completed by the end of the year.

​Calais is home to the "Jungle" camp, where thousands of people fleeing war and poverty in the Middle East and Africa are staying in the port city, hoping to reach Britain by stowing away on trucks and trains through the Channel Tunnel.

The camp and a Franco-British border control deal that effectively pushes the British frontier onto mainland France have been hotly debated since Britons voted in a June referendum to leave the European Union.

Vikki Woodfine of law firm DWF, who works with trucking companies, said the wall "is simply a knee-jerk reaction that is unlikely to make a difference in the long run."

Migrants "are increasingly desperate to cross the border and will undoubtedly find a way past it, pushing the death toll even higher in the process," Woodfine said.

​A British truckers' group said the wall is a poor use of money. Road Haulage Association chief executive Richard Burnett said Wednesday that the funds "would be much better spent on increasing security along the approach roads."

British opposition politicians also criticized the plan. Scottish National Party MP Angus Robertson said Prime Minister Theresa May should be "totally ashamed" of a proposal that echoed presidential candidate Donald Trump's call for a vast wall along the U.S.-Mexico border.

A document shown at a public meeting organized by the Port of Calais on July 6 showed the wall would be made of smooth concrete to make it harder to scale, but lined with plants and vegetation on the inside to minimize the visual impact.

France dismantled the southern half of the Jungle camp in February and March and the government said last week it would shut down the rest, but gave no timeframe.