A prominent critic of the Prime Minister will today warn that illegal migrants are costing the country at least £14billion a year in public services alone.

Dame Andrea Jenkyns will tell MPs that illegal immigration is posing an 'existential threat' to British society and security.

But she will say that it also imposes 'astronomical' costs on taxpayers which the 'vast majority' of the British public see as unacceptable.

Dame Andrea will cite official figures putting the cost of public services including health and education at £12,000 a year per person, and estimates of the illegal population at up to 1.2million.

Dame Andrea Jenkyns (pictured) will tell MPs that illegal immigration is posing an 'existential threat' to British society and security

'Even the most basic calculation puts the economic burden on British taxpayers for an illegal migration population of 1.2million at £14.4billion, just shy of 10 per cent of NHS England's budget for this year. Imagine that as a cash injection for our national health service,' she will tell a Westminster Hall debate.

In addition, she will point out, the Home Office expects to spend £482million on immigration enforcement this year along with almost £8million a day in accommodation for those who have crossed the Channel in dinghies. The Government is also giving £370million to Rwanda in its flagship deportation scheme, and will give £476million in 'handouts' to the French so they can help stop the cross-Channel boats.

'For too long, the UK has been seen as a free lunch. Study, work, marry or smuggle your way in and soon you are guaranteed a lifelong all-you-can-eat buffet for you and your extended family,' Dame Andrea will say at the Westminster session.

'Free healthcare, education, housing, social care, legal protections, and access to one of the largest charitable sectors in the world. It is demonstrably unfair to continue to ask the British taxpayer to pick up the bill.'

In addition, she will point out, the Home Office expects to spend £482million on immigration enforcement this year along with almost £8million a day in accommodation for those who have crossed the Channel in dinghies (File Image)

In order to show that the British state is no longer a 'soft touch', she will suggest tough measures to limit further arrivals and make it easier to remove people.

These will include improved surveillance and patrols along the coastline and ending further payments to France unless they stop more boats.

Dame Andrea – like former home secretary Suella Braverman and ex-immigration minister Robert Jenrick – wants Britain to pull out of the European Convention on Human Rights in order to limit legal challenges to deportation.

Dame Andrea, a minister under Liz Truss, last autumn became the first Tory MP to publicly announce she had submitted a letter of no confidence in Rishi Sunak.

She was also one of 11 rebels who voted against the Rwanda bill earlier this year on the grounds it did not go far enough.