UK Home Secretary Suella Braverman is under fire from the Opposition and refugee activists for classifying an increase in the number of refugees landing on the country's shores seeking asylum as an invasion by migrants on the border.

The Indian-origin Cabinet minister told Parliament on Monday evening that illegal migration to the country "is out of control" and that the asylum system is broken , with the sheer numbers arriving via the English Channel in small boats making it impossible to provide accommodation for all.

Her statement followed a violent incident involving a petrol bomb attack at one of the migration centres on England's southern coast over the weekend.

The British people deserve to know which party is serious about stopping the invasion on our southern coast, and which party is not, Braverman told the House of Commons.

Some 40,000 people have arrived on the south coast this year alone. For many of them, that was facilitated by criminal gangs; some of them are actual members of criminal gangs, so let us stop pretending that they are all refugees in distress. The whole country knows that that is not true. It is only Opposition members who pretend otherwise, she said.

Her junior minister in the Home Office, Immigration Minister Robert Jenrick, was forced to defend the statement saying his boss was right to be straight with the public about the "sheer scale" of illegal migration.

"In a job like mine, you have to choose your words very carefully. And I would never demonise people coming to this country in pursuit of a better life," he told Sky News' when asked about the phrase.

However, he said describing people crossing the Channel as an "invasion" was a way to show the scale of the challenge "and that's what Suella Braverman was trying to express".

The Opposition Labour Party accused the Home Secretary of using highly inflammatory language and the Scottish National Party (SNP) said such "incendiary language makes a mockery of [Prime Minister] Rishi Sunak's claims about so-called compassionate conservatism".

"No Home Secretary who was serious about public safety or national security would use highly inflammatory language on the day after a dangerous petrol bomb attack on a Dover initial processing centre," said Yvette Cooper, Labour's shadow home secretary.

The UK's Refugee Council also condemned the language used by Braverman.

To describe the serious and complex situation created by the asylum crisis as an 'invasion' is appalling, wrong and dangerous. These are men, women and children fleeing war, persecution and conflict," it said.

The Opposition has been piling pressure on the government after reports of overcrowding at a UK Border Force processing centre in Manston, Kent, on England's southern coast.

The site is only designed to hold 1,000 people, who are meant to stay for just 48 hours before being moved on, but there are currently around 4,000 migrants there. Hundreds more people were moved to the Manston facility over the weekend after the petrol bomb attack, which Braverman told MPs was not being treating as a terrorist attack.

A report in The Times' claimed Braverman blocked the transfer of asylum seekers from Manston to new hotels and ignored legal advice that the government was illegally detaining people there.

I confirm that I have not ever ignored legal advice...What I will say is this: I am not prepared to release migrants prematurely into the local community in Kent to no fixed abode. That, to me, is an unacceptable option, she said in response to a question in Parliament.

Meanwhile, British Prime Minister Rishi Sunak is being challenged over his decision to appoint Braverman as Home Secretary since he gave her the job last week, but has stood by her. She resigned from the same role in his predecessor Liz Truss' Cabinet after sending sensitive policy documents from her personal email, breaking the ministerial code.

She told MPs this week that she has been "clear I made an error of judgement...I took responsibility for it and I resigned".