People with roots in the Chagos Islands have criticised what they called their “exclusion” from negotiations leading to the UK government’s deal to give up its sovereignty of the region.

The remote but strategically important cluster of islands in the Indian Ocean is set to be handed to Mauritius after more than half a century.

Some Chagossians the BBC spoke to broadly welcomed the deal, but many said indigenous people had been repeatedly refused an opportunity to take part in talks.

The Foreign Office said the interests of the Chagossian community had been “an important part of the negotiations”.

• UK will give sovereignty of Chagos Islands to Mauritius

Pascalina Nellan, whose grandmother was born on a key island in the region – Diego Garcia, said the deal amounted to a “backstabbing” by the UK government.

Ms Nellan was born in Mauritius, where her grandmother resettled after being removed from Diego Garcia to make way for a US Air Force base.

Two years ago she moved to the UK, where she has been calling for Chagossian involvement in the deal over the territory.

“Every time we made a request to be heard we have been excluded,” she said, claiming UK officials said the Chagossian community could not be involved in negotiations between the two countries.

“Today, again, we’ve been excluded,” the 34-year-old postgraduate student told the BBC.

“We need to respect the rights of indigenous people.”

Ms Nellan said she would like to go back to the islands, but not under Mauritius’ control.

“Our right to self-determination – whether we want to be British citizens or Mauritian citizens at all – has been stripped today,” she said.

Frankie Bontemps, a second generation Chagossian in the UK, told the BBC that he felt “betrayed” and “angry” on Thursday because “Chagossians have never been involved” in the negotiations.

“We remain powerless and voiceless in determining our own future”, he said, and called for the full inclusion of Chagossians in drafting the treaty.

Steeve Bancal, a trainee social worker from Sussex, was positive about the deal.

He said Mauritius was more likely to put resettlement plans in place for Chagossians than the UK, who had “done nothing” for the community.

He expressed hope to return to the islands with his mother, who was also removed from Diego Garcia. She resettled in Mauritius, where Mr Bancal was born.

Mr Bancal said it would be a “dream come true” for his mother, 74, to return to Diego Garcia.

However, he also criticised the negotiations, saying they happened “behind closed doors”.

“None of us were told what was happening. It’s unfair on us,” he said.

“It’s our heritage – we should have had one or two people in the room.

“I don’t think the UK government trusts us.”

Isabelle Charlot was born in Mauritius to Chagossian parents, and has lived in the UK – where she is the chairperson of the Chagos Islanders Movement – for 19 years.

She said she now hoped to return to the archipelago, from which Britain forcibly removed more than 1,000 islanders between 1965 and 1973 after gaining control of the territory.

“That is what my family and I have been waiting for,” Ms Charlot told the BBC.

She said she welcomed the deal as a step toward “reclaiming [her] identity, heritage and homeland”, all of which had been “robbed” from her.

“I [knew] that the Labour government would want to right the historical wrongs and respect the international law,” she said.

Human Rights Watch (HRW) called for the Chagossians to be consulted on the deal.

Responding to the UK government’s announcement, Clive Baldwin, senior legal advisor at HRW, said: “It does not guarantee that the Chagossians will return to their homeland, appears to explicitly ban them from the largest island, Diego Garcia, for another century, and does not mention the reparations they are all owed to rebuild their future.”

Mr Baldwin called for meaningful consultations with the Chagossians.

He said unless this happens, the UK, US and now Mauritius would be be responsible for “a still ongoing colonial crime”.

Jonathan Powell, the UK’s Special Envoy for British Indian Ocean Territory negotiations, said on Thursday that Britain’s past treatment of the Chagossians was “shameful”.

But he called the agreement, reached after 11 rounds of negotiations, “genuinely historic”.

He said he could not guarantee whether Chagossians would be able to return to the islands, since they were to become Mauritian territory, but that the UK was committed to “help with resettlements if that’s possible”.

The UK government said it will also provide a package of financial support to Mauritius, including annual payments and infrastructure investment.

An FCDO spokesperson said: “This is a bilateral agreement between the UK and Mauritius.”

“We are mindful that the future of the islands is an important issue for the Chagossian community. Their interests have been an important part of the negotiations.”