Britain just got a dire warning from a group of experts about the next terrorism threat

The devastating terrorist attacks on Brussels and Paris over the last few months is a "wake up call" to how Britain is also vulnerable to similar attacks, says a prominent group of experts.

Experts that have had first hand experience with dealing with national security - told The Telegraph newspaper in an open letter on Tuesday that Britain needs to tighten its borders if the country wants to remain safe.

"Irrespective of whether Britons vote to leave the EU on June 23, we urge the Government to review security at our borders. We would support any new measures to tighten up procedures in order to make Britons safer in an ever more uncertain world," said the group.

"These could include better sharing of intelligence about potential extremists from other EU countries, and the maintenance of proportionate communications data provisions necessary to protect Britain from attack."

The group who signed the open letter were:

• Lord Stevens of Kirkwhelpington - Metropolitan Police Commissioner, 2000-04.
• Lord Carlile of Berriew QC - Government's Independent Reviewer of Terrorism Legislation, 2001-11.
• Sir Paul Stephenson - Metropolitan Police Commissioner, 2009-11.
• Sir Hugh Orde - President, Association of Chief Police Officers, 2009-15.
• David Davis MP (Con) - Shadow Home Secretary, 2003-08.
• Richard Walton - Head of Counter Terrorism Command, Metropolitan Police, 2011-15
• Peter Higgins - Director, UK Immigration Service (Ports), 1999-2002

"There are terrorists mixing in with asylum seekers"

In a separate interview with The Telegraph, Higgins warned about how the lack of stringent checks on documents is letting terrorists mixing in with asylum seekers.

"The controls for EU citizens are pretty minimal. The Border Force glance at your passport and wave you on," said Higgins.

"All you can do is check that they have the right documents to prove they are EU citizens, you can't even spend a lot of time checking whether their documents are false. You are getting people coming in as part of the huge flow of migrants, there are terrorists mixing in with asylum seekers."

Higgins' comments echoed what happened in Paris, France in November last year where 130 people were killed in gun and bomb attacks on a sports stadium, bars and a concert hall. It was the deadliest militant assault in Europe since 2004.

One of the bombers who carried out the Paris terrorist attacks entered Europe as a Syrian migrant, according to foreign officials.

The group of experts cited EU agency Frontex data to highlight how migrant activity is alarming for Britain.

It said in the letter to The Telegraph that "EU member states reported a record 1.82 million illegal border crossings last year - six times more than in 2014. Our own National Crime Agency found that migrants have been paying people-traffickers to find new ways to avoid tighter security at Dover and Calais."