Priti Patel has been accused of trying to deport a former senior Iranian police officer who fled to the UK after giving first-hand testimony of potential human rights violations by the Iranian government.

Counsel for the Iran Atrocities Tribunal –also known as the Aban Tribunal – in London has written to the home secretary saying that a named former officer in the Iranian police has been detained in the UK and been told he will be sent 4,000 miles to Rwanda next week.

In a letter seen by the Guardian the counsel claims the former officer fled to the UK in May after being sentenced to five years in an Iranian prison for refusing orders in 2019 to fire indiscriminately upon crowds of protesters.

Patel announced last week that the first deportation flight to Rwanda would leave on 14 June. Lawyers believe the flight may be delayed because of legal challenges.

Hamid Sabi, counsel to the Iran Atrocities Tribunal, wrote that the former police officer arrived in the UK on a small boat on 14 May 2022 and is now detained in Brook House detention centre at Gatwick. On 31 May, he was served with notice that he would be sent to Rwanda, the letter claimed.

“[The former police officer] is a conscientious and brave citizen of the world, and he has a genuine and well-founded fear of persecution in Iran. Iranian agents were seeking his whereabouts while he was in Turkey by harassing his family members. Rwanda, having a close relation to the Islamic Republic of Iran is not a safe haven for [him]. Please reconsider your decision for his removal,” Sabi wrote in his letter to Patel.

The former officer told the tribunal he was in charge of dozens of officers in a provincial city when he was ordered by the authorities to shoot at peaceful demonstrators.

According to the letter, he was tried before a disciplinary court in Iran for disobeying the order to shoot and was sentenced to five years.

He fled from Iran to Turkey in the autumn of 2021 and testified by video link before the tribunal in November, the letter said.

On 15 November 2019, the Iranian government had announced that fuel prices had tripled, leading people to protest in the streets. The nationwide protests were peaceful and only consisted of motorists blocking roads with their cars and people shouting slogans.

Over the week that followed, protests in most cities, towns and provinces were repressed by police and military forces, who attacked protesters and bystanders with firearms. Hundreds of people were killed and thousands more injured, arrested or tortured.

The Iran Atrocities Tribunal was set up by three NGOs to examine evidence of human rights violations in Iran during late 2019.

The Home Office has also been accused of attempting to deport unaccompanied 16-year-olds to Rwanda in the first wave of asylum seekers.

One person who said they were under 18 was placed in detention awaiting potential deportation to Rwanda and only released at the end of May, after intervention from lawyers.

Another two asylum seekers identified by one charity as having been warned of imminent removal, and now held in immigration detention centres, say they are 16, but their age is contested by the Home Office.

Those currently detained to be sent offshore include Syrians, Sudanese, Afghans, Eritreans, Iranians and Iraqis, some of whose home countries are active conflict zones.

A group of asylum seekers facing being sent to Rwanda started a hunger strike last week, and on Friday dozens of people in Brook House detention centre near Gatwick airport started a protest in the exercise yard.

A Home Office spokesperson said people should not make dangerous and illegal journeys to the UK, adding: “We remain fully committed to working with Rwanda to offer safety to those seeking asylum.”