A key witness in a student visa fraud trial has accused the Home Office of betraying him by now threatening him with deportation.
Indian national Sameer Shaikh, who currently lives in East Ham, was assured he would be protected if he gave evidence in court against a former employer in a high-profile student visas fraud.
However his applications to stay in the UK have since been rejected and he faces being sent back to India.
The man he helped prosecute, Fassiuddin Mohammad, who ran agency Bright Consultant Services, fled to his native India before the trial and Sameer fears his life could be at risk if he is forced to return his homeland.
He said: "Sometimes I don't sleep for nights - I feel so helpless, I feel so annoyed - but then I promise myself, 'you have to fight for this' so that what happened with me shouldn't happen with some other witnesses or other people in their life.
Accusing the government of failing in its duty to protect witnesses, he added: "That's what I'm fighting for: justice and a fair and transparent system."
East Ham MP Stephen Timms, who repeatedly lobbied the Home Office for the past two years, told the Recorder: "I am troubled by Mr Shaikh's case, which is very unusual.
"I have raised the matter with ministers at the Home Office, but have not yet received a satisfactory explanation.
"In my view, promises made to him by the UK authorities, and which he accepted in good faith, should be honoured."
Sameer - who suffers depression, anxiety and other health conditions - says the ordeal has left him suicidal at times, with his GP expressing concern for his mental wellbeing and "risk of serious physical harm" if he returned to India in a letter supporting him.
He originally sought asylum in the UK in 2012, and claims he was blackmailed to become involved in the fraud and sat English language tests on behalf of a few others.
He later agreed to plead guilty to charges of criminal conspiracy to breach immigration rules and then give evidence for the prosecution.
Over the months that followed and when his employer Fassiuddin Mohammad fled to India before the trial, Sameer received assurances, particularly from one Home office crime team officer that he would be protected if he gave evidence.
The officer internally secured Sameer a temporary visa to allow Sameer to stay in the country until after all legal proceedings had concluded.
Sameer gave key evidence during the trial in April and May 2016.
After the trial, Sameer was led to believe for almost a year that the officer would internally apply for indefinite leave to remain for him but as the July 2017 expiry date of his temporary leave to remain approached, the officer cut all contact.
"The people that dealt with me for two years, who gave me hope, promises, expectations, they just left me," Sameer said.
"They have a duty to protect their witnesses at all times - before, during and after the case.
"If a senior immigration officer, who is in position of power and trust and responsibility, gives me promises, assurances, hope - I had reason to believe that he was going to get me indefinite (leave to remain) internally - why should I doubt him?"
Sameer received an email on July 20, 2017, days before the end of his visa, telling him he needed to make his own application and the officer could not do anything to help other than provide a letter of support.
The letter stated that the convictions secured in the trial were "in no small part due to the evidence supplied by Mr Shaikh" and that Sameer gave evidence "despite knowing that there may be repercussions from within his own community and from associates of the criminal network in India."
Sameer applied for indefinite leave himself but his application was refused in February 2018. The refusal meant that if Sameer did not appeal the decision and stayed in the UK, he could be deported.
A review hearing is scheduled for July 1.
Sameer said: "I have promised myself I will fight for justice now and I will not give up.
"I have evidence and the strength to tell the world, so why shouldn't I do that?
"It's about right and wrong."
A Home Office spokesman said: "As legal proceedings are ongoing, it would be inappropriate to comment."
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