The Harvard scholar, who was elected prime minister in April 2011, added he hoped a leadership transition in Beijing this year would bring a "new perspective" on Tibet.
More than 30 people have set themselves on fire in Tibetan-inhabited areas of China since the start of March 2011 in protest at what they say is religious and cultural repression by the Chinese authorities.
"It means the situation is not bearable," Sangay, 43, told the Sydney Morning Herald on a visit to Australia.
"It's not just that it's a desperate act, but also a political act," he said.
"Peaceful protests, peaceful rallies are not allowed. The statements they leave behind consistently say they want freedom.
"The self-immolations are somehow an assertion of freedom -- 'you can restrain my freedom but I can choose to die as I want'."
China blames spiritual leader the Dalai Lama for inciting the self-immolations in a bid to split Tibet from the rest of the nation, and insists Tibetans now have better lives due to Chinese investment.
In an address to the National Press Club, Sangay said the spark for self-immolations was 2008 anti-government riots in Lhasa -- unrest that subsequently spread to other Tibetan-inhabited areas of China.
"Since then, instead of responding positively or liberally, unfortunately the Chinese government has clamped down more," he said, adding that the Tibetan capital was essentially closed to the outside world.
"The military walk up and down the streets and there has been an intensifying of the campaign to demonise the Dalai Lama," he said.
"How would you feel if you revered someone and you were asked to denounce him by standing on his picture or badmouthing him?
"These are the reasons why Tibetans are taking these drastic actions."
Most of the self-immolations have occurred since Sangay was elected, four months before he took office to assume political duties being relinquished by the Dalai Lama at the head of the India-based exiled government.
Asked if this showed that Tibetans feel more hopelessness as the Dalai Lama restricts his political activism, or whether it was an effort to push Sangay to take a harder line against China, he replied: "It's too early to tell."
Sangay added: "We have repeatedly asked them not to take drastic actions, including self-immolation, but they continue to do so."
Despite China's consistently hardline stance on Tibet, the exiled minister said he was hopeful that change could occur with a new leadership.
"Given the past 50 years of experience, we haven't had much reason for optimism, but as a human being I remain hopeful about the new leadership led by Xi Jinping," he said.
Chinese President Hu Jintao, Premier Wen and five other leaders are due to relinquish their positions on the nine-man Standing Committee at a congress later this year that will also announce their replacements.
Vice President Xi and Vice Premier Li Keqiang are expected to be the only current members of the standing committee who will stay on -- replacing Hu and Wen respectively.
"Hopefully with new people, there will be a new perspective on Tibet and hopefully we'll have better days ahead," said Sangay.
But Xi has previously appeared to dash the hopes of anyone hoping for a change of course from China's leadership.
In a speech last year he vowed to fight "separatist activities" in the region and said Beijing should "smash any attempt to undermine stability in Tibet".