A British man who was stripped of his citizenship by the Home Office for almost five years has described the “devastating” impact of the decision as the government pursues fresh powers to remove a person’s citizenship without warning.

The 40-year-old, who was born in London, returns to the UK this week after being stranded in Bangladesh since 2017 when the Home Office served a deprivation of citizenship order on him shortly after he flew to the country for the birth of his second daughter.

E3, as he is referred to in court documents, was working in the UK when he travelled to Bangladesh but not earning enough to sponsor his wife to join him and has since been stateless and destitute with his wife and three daughters.

According to the Home Office’s deprivation order, the Briton was “an Islamist extremist who had previously sought to travel abroad to participate in terrorism-related activity” and that he posed a threat to national security.

Although the UK government has reinstated his citizenship, his lawyers say they have received no explanation or any specific details to support the claims. E3 has never been charged with any criminal offence in the UK or elsewhere.

E3 told the Observer: “The allegation against me is so vague that it even suggests that I only tried to travel to some unknown destination to take part in an unspecified activity related to terrorism.

“How on earth do you defend yourself against an allegation like that, especially when the government relies on secret evidence? The disclosure my solicitors received was almost entirely redacted so I have no idea what the government is referring to.

“Why was I not arrested and questioned? Why have I been punished in this way without ever being shown a single piece of evidence against me? The government should admit that they have made a mistake and own up to it.”

The Home Office had accused E3 of being ‘an Islamist extremist’.

It comes as politicians consider controversial plans contained in the contentious nationality and borders bill, which is going through the House of Lords, to allow the Home Office to remove someone’s citizenship without the need to inform them.

The plans have prompted warnings that ethnic minorities could be treated differently from white Britons for committing the same crime.

“Being left stateless and not knowing why I was suddenly stripped of my citizenship had an extremely adverse impact on my mental health. It was the most depressing period of my life,” said E3.

“Being British is a fundamental part of my identity, but it really feels like you need more than just being born and raised in the UK to really be considered one. Having an ethnic background relegates you to being a second-class citizen,” he added.

Fahad Ansari, his lawyer at Duncan Lewis, said: “My client lost five years of his life because of the unlawful decision of the home secretary that lacked any prior judicial oversight.”

During E3’s period of statelessness in Bangladesh, his wife gave birth to another child in 2019, but because E3 was not considered British, the child was denied British citizenship.

Despite her father’s citizenship being reinstated, the Home Office is refusing to accept that the daughter is a British citizen.

The high court has granted E3 and his daughter permission for a judicial review of that decision and a hearing is expected in the spring, with E3 saying that one of the main reasons for returning to the UK was to help the legal fight as well as to see his frail mother.

Ansari said: “We will continue fighting for his baby daughter to be recognised as a British citizen as is her legal right so that she can join him in the UK.”

The case also has ramifications for many children stranded in the refugee camps in Syria, who were born after their parents were deprived of their citizenship on the same basis as E3.

Anas Mustapha, communications manager of advocacy group Cage, which is assisting E3’s family, said: “E3’s case brings into sharp focus the devastating impact of citizenship deprivation and its often forgotten victims, the children of those deprived.

“E3 has been successful in overturning the decision but many others must reckon with the state-imposed exile as it is impossible to meaningfully challenge it due to the use of secret evidence.”

E3 married in Bangladesh in 2013 and his first daughter was born a year later. Working in the UK and sending money to his wife in Bangladesh, he travelled to be with her on 19 April 2017 for the birth of his second daughter. His two older daughters have British citizenship.

On 3 June 2017, a deprivation of citizenship notice was sent to his mother’s London address – the day before E3 was due to return home. The Home Office followed it up with a call to his mother informing her that E3 would not be able to return to the UK.

E3’s British citizenship was restored following a judgment that he had effectively been left stateless because he could not have Bangladeshi citizenship like his parents: he forfeited that right by not claiming it by the age of 21.

Speaking to the Observer on the eve of his return to London, E3 said that he could not wait to see his mother but felt “very sad” at leaving his wife and daughters behind and facing an uncertain future.

He said: “I have also missed taking long walks in the UK countryside, getting out to the beach in the summer, watching Match of the Day with my friends, and just the general sense of humour everyone has there. There is nothing quite like British sarcasm.”

The Home Office has been contacted for comment.