It comes after the government announced it would give up sovereignty over a cluster of remote Indian Ocean islands, a move which follows years of diplomatic talks and international pressure on the UK to resolve their disputed status.
Meanwhile, Chagossians who oppose the deal to hand control of the islands to Mauritius have staged a protest outside Parliament.
He told the Commons the status of the Falkland Islands, Gibraltar and other British Overseas Territories are "not up for negotiation".