Free Tibet has demanded that the Prime Minister disclose whether the issue of human-rights violations in Tibet was raised during the visit by Chinese Prime Minister Wen Jiabao earlier this month.
The charity is awaiting confirmation from Number 10 that Tony Blair pressed for the opening of negotiations between the two countries. This year marks the centenary anniversary of the invasion of Tibet by the British, when 3,000 Tibetans were killed by British troops.
Anne Callaghan, campaigns manager for Free Tibet, said: "The Government has a debt to the people of Tibet to press for the country's right to decide its own future."
The Dalai Lama will visit Britain between 27 May and 3 June, but has been unable to secure an audience with Tony Blair. He will meet with the foreign secretary Jack Straw instead.
Formal contact between Beijing and the exiled Tibetan government reopened in 2002 after more than 10 years of diplomatic stalemate. Free Tibet says that international pressure is vital to ensure that China abandons its preconditions for talks, which include the recognition of Tibet as part of China.