In all, it would encompass about 2.4 million sq km where a large number of other ethnic groups have lived together with the Tibetans for centuries.

Only half of the 6 million existing Tibetans live in the autonomous region, while others live in the bordering provinces. Many live in Nepal or India.

Tibet expert Melvyn Goldstein points out in his book The Snow Lion and the Dragon that a politically united Greater Tibet has never existed. Historically, the Dalai Lama seldom extended his administrative control beyond the boundaries of the Tibet Autonomous Region.

In 1728, the Qing government had finalised Tibet's administrative border, placing the large ethnic Tibetan areas in Kham and Amdo under the jurisdiction of other provinces. The idea of a united Greater Tibet was raised by the 13th Dalai Lama, who tried to push for it after the collapse of the Qing dynasty.

In 1913, Britain, which wanted to create a buffer state in Tibet, put pressure on the newly formed Chinese republican government to attend a meeting with British representatives and delegates of the Dalai Lama in Simla, northern India. The 13th Dalai Lama raised the question of Greater Tibet at the conference but it was angrily rejected by Beijing.

Britain itself did not want to see a fully independent Tibet. The final draft of the Simla Convention was a compromise, which declared that Tibet would be autonomous but also acknowledged China's sovereignty over the region, according to Professor Goldstein.

But because of the 13th Dalai Lama's insistence that the autonomous region cover all areas populated by Tibetans, Beijing refused to ratify the convention, and it was left unsigned.

It has become the thorniest part of the Tibet issue ever since.

Tibetans championing the idea argue that people in the areas share a similar culture and religion. Designated Tibetan autonomous areas - where an ethnic minority comprises half the population - account for half of Sichuan, 10 per cent of Gansu and 10 per cent of Yunnan. In Qinghai, a quarter of the population is Tibetan.

Beijing refuses even to contemplate such an idea. The areas in question, it argues, were never dominated by a single ethnic group. Apart from Tibetans, Mongolians, Hui Muslims, Han Chinese, Qiang people and many other ethnic groups have settled in the areas for generations.

Xinhua has likened the Greater Tibet proposal to a 'racial cleansing policy' and cited it as evidence of the Dalai Lama's 'splittist intentions'.

Just last week, Foreign Minister Yang Jiechi blasted the 14th Dalai Lama for holding on to the idea.

'The Dalai side still insists on establishing a so-called Greater Tibet on a quarter of China's territory,' Mr Yang said on the sidelines of the annual meeting of the National People's Congress in Beijing.

'They want to drive away the Chinese armed forces on Chinese territory and ask all non-Tibetans to relocate themselves, people who have long spent their lives in that part of Chinese territory. You call this person a religious figure?'

While the demand for the creation of a Greater Tibet may be politically unrealistic, the vision of a Tibet uniting Tibetans living in different areas has brought exiles together. It would be politically impossible for the Tibetan government-in-exile to give up on the proposal, especially given that many of its key members come from Tibetan-populated areas outside the Tibet Autonomous Region.

Professor Goldstein, in The Snow Lion and the Dragon, writes: 'Tibet had not ruled most of these areas for a century or more, and it is difficult to see how China could have handed over large areas in Sichuan, Qinghai, Gansu and Yunnan, many of which included [Han] Chinese and Chinese Muslim [Hui] populations that had migrated there well before the Communists came to power in 1949.

'However, if Dharamsala [the seat of the exiled government] decided not to pursue a demand for a Greater Tibet, it would be breaking faith with the eastern Tibetans in exile. Like the forsaking of independence, this issue was highly contentious and if it became known that the Dalai Lama was willing to consider it, the unity of the exile community could be permanently split.'

But while the concept of Greater Tibet looks near-impossible politically, it is hard not to include these bordering areas outside the Tibet Autonomous Region when addressing the Tibet issue. Much of the unrest that has gripped western China over the past decade first fomented in such areas. In March last year, many rioters in Lhasa were Tibetans from nearby provinces.