Under a new scheme, ministers can reject claims from those with ties to a safe third country.
The move occurred mainly between January 2021 and September last year.
That means they are automatically rejected for asylum in Britain.
As it emerged that processing figures have hit record highs of 160,000 this week, the Sun on Sunday can reveal just a fraction of those identified as being immediately ineligible have been deported.
Of 20,605 that could be booted out under the rules, the latest figures show that only 21 have so far been deported.
Most came from Albania, with 2,347 claims rejected, followed by Eritreans (2,321) and those fleeing Iran (2,167).
Some 18,494 have been told they will be booted out but just 21 – or one in every thousand – have successfully been removed.
Those that were booted out were sent to Denmark, Germany, Ireland, Italy, Slovenia, Spain, Sweden and Switzerland.
Tory MP Jacob Rees-Mogg said: “When there are such simple cases you would hope that would be done as an immediate priority.”
That needs to be done as soon as possible to get control of the numbers.
“It is simply mystifying that the Home Office has not done more to deal with this.”
Labour’s Yvette Cooper said: “This shows the law the Tories passed has made things worse not better, and was just a complete con.
“All it has done is add to the delays and add hundreds of millions of pounds in hotel costs.
“Labour has a common-sense plan to crack down on the criminal gangs to prevent dangerous boat crossings and to speed up the asylum system to prevent inappropriate hotel use.”