Ben Fogle has insisted he will charter a boat and take exiled islanders back to their homeland if the Government refuses to "right a terrible, terrible wrong".

The adventurer and television presenter also suggested the Whitehall attitude to the Chagos Islands - a British-controlled overseas territory - struck him "as a form of racism" when compared to the help given to the Falkland Islands.

He led a Chagossian delegation into Downing Street to deliver a petition calling on David Cameron to make amends for the "crime against humanity" carried out by previous governments by allowing islanders to resettle as soon possible.

The British forced the Chagossians to leave the islands, in the central Indian Ocean, by 1973 to allow the US to establish an air base on Diego Garcia.

Critics described the expulsions as one of the most shameful episodes in modern British colonial history, with the exiled Chagossians fighting a long series of legal battles for the right of return.

In March, the Government delayed a decision on resettlement despite vows to reach a decision before the end of the last Parliament.

The deal which allows the US to maintain a base at Diego Garcia also comes up for renewal next year.

Exiled islanders and their supporters held a protest in Whitehall today before and after the petition hand-in with many arriving from Crawley, which is home to a large Chagossian community.

Speaking outside No 10, Fogle said he remains hopeful despite setbacks over the years.

He told the Press Association: "We've got the renewal coming up for the lease on the island, we've got a new Cabinet and a Prime Minister who has got another term - in my mind this is a chance for Cameron to do something that will be a long-lasting legacy to right a terrible, terrible wrong.

"No-one can hear this story or read about this story without understanding how wrong it is. I've never met anyone that agrees that it was right."

Fogle, who is a patron of the UK Chagos Support Association, said he had visited the islands and suggested Whitehall was wrong to believe resettlement requires building facilities similar to Britain.

He said: "It's a totally different infrastructure. I will quite happily, if we hit another wall with our Government saying no, I'll do it myself.

"I will take the islanders back. I will charter a boat. We'll build a camp and we'll live there. It's as simple as that.

"I've done it for 15 years now campaigning and we think we make some headway, and we don't.

"I'm being an optimist right now. We've handed in a petition - 2,600 signatures isn't too bad, it's not the millions you get to save Jeremy Clarkson, but it's only because people don't know the story and the reason for being here today and coming to Downing Street - campaigning and demonstrating outside is to try and tell everyone in this country what our Government did to these people."

He went on: "It wasn't this Government, it was a Tory government, but I don't understand why we were willing to go to war to protect a couple of thousand Falkland Islanders and yet we won't allow the Chagossian people a right to return to their island.

"They are all overseas territories, there are military bases on all of them - there's a huge military base on the Falkland Islands for goodness sake - it strikes me as a form of racism. It's the only deduction that I can get.

"I've tried to work out what else it can be but that's the only thing I can deduce from it."

Sabrina Jean, chairwoman of the Chagos Refugees Group UK, said: "I'm very excited and I have a hope we will return back home very soon.

"On the petition we have 2,660 signatures and we speak about our life here in the UK, how it is and also I told the Prime Minister he needs to consider the Chagossians in the UK also - if not, he needs to return us back home."

Ms Jean said it was important for action to take place, explaining: "It's the same Prime Minister who has been elected again and for us it's just good to continue our fight because if Labour had been elected it would take long and long and long (for a decision)."

She added: "I'm giving them 15 days to one month to reply to me, if not they will hear from us again."

Stefan Donnelly, chairman of the UK Chagos Support Association, said the focus needs to remain on the islanders in the months ahead.

He said: "It's a very important year for the Chagossians generally.

"The Government had indicated they would decide whether to support return before the election, they failed to do that, there's been no time-scale given on that and this really needs to get sorted in the next year - not least because the agreement on the use of Diego Garcia by the US expires in 2016.

"There's also the issue of the Mauritian government and the dispute over the marine protected area.

"So all of these decisions need to be made over the next year so what we hope today will do is maintain that the real focus needs to be on the Chagossian people and their rights to go back to their land."

A Foreign Office spokesman said: "The Government is committed to its ongoing review of resettlement policy towards the British Indian Ocean Territory.

"The 2015 independent feasibility study on resettlement delivered by consultants KPMG showed there are fundamental uncertainties around how resettlement could work, potential costs and the likely demand from Chagossians for resettlement.

"Consequently, further detailed work is under way to understand these uncertainties and develop various options to enable a ministerial decision on the way ahead in due course.

"Work to date has taken into account Chagossian views and the Government welcomes ongoing dialogue with the Chagossian community during and beyond this policy review."