Andrew Tingley, an immigration lawyer at Kingsley Napley, said it was "beyond farcical" that new rules requiring foreign nationals from outside the EU to have a biometric residents permit had left the IT system unable to cope.
The system that was introduced was not fit for purpose. It was close to collapse a few weeks ago. It has now collapsed. It's an absolute mess.
Mr Tingley also warned of the impact on the UK's economy.
You have senior global managers and directors of companies saying, 'enough is enough'. Employers are saying they can't access a reasonable immigration system and they're considering moving abroad.
They've come to the point now where they're seriously considering not investing or working in the UK because they can't access any reasonably competent system.
More top news
Two ambulances crashed leaving one driver dead and three people seriously injured.
A scandal-hit NHS trust where a teenager drowned in the bath is still failing to protect patients from risk of harm, a watchdog has found.
New research suggests metal-on-metal hip replacements implanted since 2006 are more prone to failure and they "fail in a much nastier way".