MPs and lawyers are demanding an independent investigation into the government’s newly outsourced visa system after it emerged private firms were raking in millions of pounds as vulnerable people are forced to pay “extortionate” fees and travel long distances to apply for UK status.

Cross-party politicians have backed calls for an urgent review into the Home Office’s partnership with French firm Sopra Steria following warnings legal migrants risked being “thrown into the hostile environment” after the visa processing service was outsourced to the company last November.

The Independent reported earlier this week that the new system – under which applicants must attend one of just six “core centres” across the country which offer a free service, or another 51 which charge a fee starting from £60 – was forcing people to travel hundreds of miles or pay high fees in order to submit their applications on time due to a lack of free appointments.

Labour, the Liberal Democrats and the Green Party have since written to the National Audit Office (NAO) requesting that they conduct an investigation to provide parliament with a report on the operation of the contract.

In a letter to the watchdog, Labour MP Paul Blomfield said this would enable MPs to “scrutinise effectively the services provided by Sopra Steria, which thousands of our constituents will require”.

“I remain extremely concerned about [the firm’s] capacity and ability, particularly as we approach the inevitable increase in demand that will result from the ‘student surge’ period in September 2019 and applications for the EU Settlement Scheme,” said Mr Blomfield in the letter.

An NAO spokesperson said they had received the letter and would be “considering its contents carefully” in the coming days and deciding how best to respond to the concerns it raises.

The demands have been backed by the Law Society and the Immigration Law Practitioners’ Association (ILPA), which represent solicitors and barristers across the country. Both have previously raised concerns with the Home Office about their misgivings with the system.

Christina Blacklaws, president of the Law Society, said: “Given the problems which have been raised by us and by others it makes sense at this point for the operation to be subject to independent scrutiny. We are extremely concerned inconsistencies in the process could lead to unlawful or incorrect decisions for applicants.”

Cross-party politicians including shadow immigration minister Afzal Khan, Liberal Democrat home affairs spokesperson Ed Davey, Green Party co-leader Jonathan Bartley and Labour MP David Lammy have backed the demands.

While visa applicants could previously go to their local post office to provide biometric data such as fingerprints, they must now attend one of the six offices in the UK that offer a free service, located in Manchester, Birmingham, Glasgow, Cardiff, Belfast and Croydon.

There are another 51 centres, mainly based in local libraries, which charge a fee starting from £60. Sopra Steria also offers a “premium service” through a partner company called BLS, where appointments start at £200. The service made more than £2m between January and April 2019, according to data obtained through a freedom of information (FOI) request.

Solicitors said applicants had been unable to book free appointments due to a lack of availability on Sopra Steria’s website, with some forced to travel hundreds of miles or pay high fees – sometimes the premium option – in order to submit their applications on time.

In one case, a disabled Pakistani refugee in Manchester was repeatedly unable to book a free appointment for his leave to remain application due to a lack of availability. The only alternative offered to Abdul Farooq, 56, was to attend the premium lounge in London at a cost of £780.

His local MP Afzal Khan, said this was a ”laughably high sum” that his constituent ”just can’t afford”, adding: “UKVCAS appointments are compulsory, but too frequently entirely unavailable outside of London. Sopra Steria is putting profit above people, and the Home Office should urgently review its partnership with the company.”

In other cases, applicants have been met with a “maze of misinformation and misdirection” while completing the new online application forms provided by the firm, which lawyers said had led people to abandon the process or submit inaccurate applications, potentially leading to erroneous refusals.

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Mr Davey of the Liberal Democrats said it was a “scandal” that private firms were “profiteering” from fees for visa applications, adding: “People who come to our country bring massive benefits for our economy and our society. We should welcome them, not set up huge financial barriers.”

Labour MP Ian Murray raised concerns about the fact that there is only one centre offering free appointments in Scotland, saying it “completely misunderstood the geography” of the country and that it was “just another example of the hostile environment” created by the Home Office.

Mr Lammy said it was a “national disgrace” that the visa system was being outsourced to private firms for profit, saying it created an “outrageous additional barrier” to an “often already systematically unfair” process.

“Many of those who cannot afford to pay exorbitant fees or travel vast distances have every right to remain in the UK. This grubby system is forcing them to endure all the indignities of the hostile environment,” he added.

A Sopra Steria spokesperson said their locations were designed to give 78 per cent of applicants access to a centre within 50 miles and 62 per cent access to a centre within 25 miles.

They said they had expanded their capacity, with seven additional service points set to go live by July 2019, including a second core location in Manchester, in response to consumer demand.

A Home Office spokesperson said: “We are sorry for any inconvenience caused to those unable to access appointments, which have been subject to a higher than expected demand.”