Preparations are being made for the deportation of a number of Jamaican nationals who came to the UK as children, in an apparent reversal of an earlier agreement not to deport people who arrived in this country as minors.

A charter flight to Jamaica is scheduled for 11 August, returning several dozen people whose criminal convictions have triggered deportation orders. However campaigners have protested that it is unreasonable to remove people who have spent a lifetime in the UK to a country where they no longer have any ties.

Last November the Home Office made an agreement with Jamaican officials not to remove people who came to the UK under the age of 12, according to Jamaican high commissioner Seth Ramocan. “They have consented to having an age limit. It’s a request that has been granted,” he told the Guardian last year. It is not clear whether this concession was granted only for the last Jamaica deportation charter in December, amid strong public pressure against the flight, with support from Bernardine Evaristo, model Naomi Campbell and historian David Olusoga.

One of those booked on next week’s flight arrived as a two-year-old child, and now aged 23, is being deported for a drugs offence. “It feels unfair to send me back to a country I don’t know,” he said by telephone from Colnbrook immigration removal centre, asking to remain anonymous. “I did nursery, reception, primary school, and secondary school in England. I haven’t been in an aeroplane or left here since I was two.”

He acknowledged that he had committed the drugs offence, but said he had already completed his two-year sentence, and felt the deportation represented a double punishment. “I’m not really a foreign criminal because I’ve spent all my life here. Everything I learned, I learned in England,” he said. He will leave a two-year-old son and an unwell mother in England.

In 2018 a Home Office-commissioned report from the former prisons and probation ombudsman Stephen Shaw, called for a new approach to the policy of detaining and removing people who had committed crimes but lived most of their lives in Britain; the Home Office has not implemented the recommendation.

Karen Doyle, of Movement for Justice, an immigrant rights campaign organisation, has spoken to 19 people due to be deported next week, six of whom came to the UK under the age of 12 and five of whom spent some of their childhood in the British care system. She said at least three of those who arrived in the UK as minors (one of whom arrived as a three-month-old baby) had had tickets on the deportation flight cancelled in the past 48 hours, but several others who came to Britain as children are still scheduled to be removed.

“There is very little public support for deporting people who were raised in the UK, in British schools and in our care system, to countries they don’t even remember,” she said.

Bella Sankey, director of the charity Detention Action, noted that many of the men and women scheduled to leave on the flight “were brought to the UK as children and are as British as the union jack. The Jamaican government should insist the UK upholds its agreement to stop deporting this group. There is no valid reason for this inhumane practice.”

The Home Office and the Jamaican high commission have been approached for comment.