The Ministry of Justice has revealed 80 foreign nationals serving life or indeterminate sentences in England and Wales have been sent back to their home countries to serve out the remainder of their jail terms since 2015.
Eleven of those were Albanian nationals, the MOJ said in response to a request made by Sputnik News under the Freedom of Information Act.
But one of those 11 was Hekuran Billa, who was sent back to Albania in 2016, only to be released by a judge.
Norman Brennan, a retired London police officer and leading law and order campaigner, said: "While it is good for these people to be sent back to their home countries because it frees up space in our prisons, one would expect them to serve the whole of their sentences in those countries.”
He added: "If they are not, why not? And if that is the case why are they being let out when they could pose a serious threat to their own citizens?”
Earlier this year it emerged Billa - who had been convicted of murder and jailed for a minimum of 34 years in London in 2008 - had been sent back to Albania and then released.
In October 2006 Billa - using the false name Herland Bilali - gunned down Prel Marku, a 22-year-old bricklayer in an Albanian social club in Park Royal, west London.
In June this year Billa, 40, was shot dead at the rental car business he owned.
Mr Brennan said: “What are we doing sending them back to their own country when they are not serving their sentences or it’s being reduced? This sort of case undermines the criminal justice system, which is a mess.”
The MOJ also revealed 60 foreign nationals were jailed for life in 2019, an increase on 48 the year before and up from 36 in 2015.
Of those 59 had been convicted of murder.
The whole criminal justice system is an utter mess and the government needs to get its act together.”
Among those convicted of murder in 2019 were Dariusz Kaczkowski, 33, and Mariusz Skiba, 32, who stabbed another Polish national to death in a car park in Boston, Lincolnshire.
Przemyslaw Cierniak, 41, was knifed after he begged for £1 from the pair, who had gone down an alleyway in the town centre to take amphetamine and drink alcohol.
Estonian national Kirill Belorusov, 32, was jailed for life in 2019 for murdering his ex-girlfriend, French film producer Laureline Garcia-Bertaux, 34, whose body was buried in a shallow grave in the garden of her London home.
Belorusov fled to Estonia and sent fake text messages to her friends and family in a bid to pretend she was still alive.
Also jailed for life in 2019 was Jairo Sepulveda-Garcia, 36, a Spanish national, who stabbed a fellow Spaniard to death at a squat in east London after the other man accidentally nicked him with some clippers as he cut his hair.
Mr Brennan said the recent influx of illegal immigrants from Syria and elsewhere who had crossed the English Channel from France in boats was a major cause for concern, when some of them may have committed crimes abroad.
But he also said he hoped that, following Brexit, the UK authorities would be able to stop EU nationals with serious criminal records from entering Britain.
Mr Brennan said: "There must be far more stringent measures put in place to stop foreign nationals with criminal records getting into Britain."
The Ministry of Justice also revealed that between 1 May 2014 and 31 May 2019 a total of 233 British nationals had been sent back from abroad to serve their sentences in prisons in England and Wales.
It is understood the majority of those were from prisons in Spain and the Republic of Ireland and they included only a handful of murderers.