China has branded Taiwan's President Chen Shui-bian a "troublemaker and saboteur" for a speech hinting at formalising Taiwan's independence.
President Chen has signalled a harder line towards China
Mr Chen suggested last month that it might be time to consider scrapping Taiwan's guidelines on unification.
In China's first official response, a spokesman said such a move would break a promise made by Mr Chen in 2000.
China sees Taiwan as its territory, threatening to use force if the island moves towards formal independence.
Mr Chen suggested late last month that the time had come to seriously consider scrapping the National Unification Council and its National Unification Guidelines, in a speech which created diplomatic and political shockwaves.
The Council was set up in 1990 as an attempt to convince the Chinese authorities that Taiwan was committed to reunification, and it helped kick-start landmark talks between the two sides in the early 1990s.
Mr Chen's independence-leaning Democratic Progressive Party (DPP) has always opposed the Council, but Mr Chen promised when he first took office in 2000 that he would not scrap it or its guidelines.
Correspondents say Mr Chen's speech was signalling a harder line towards China, although Taiwanese government officials have tried to play down the comments.
On Wednesday, Li Weiyi, spokesman for China's Taiwan Affairs Office, said Mr Chen's speech showed he remained committed to moving the island towards formal independence.
Mr Li said Mr Chen was "the troublemaker and saboteur of cross-Straits ties and Asia-Pacific peace and stability".
Taiwan's government responded swiftly to the comments.
Joseph Wu, head of Taiwan's Mainland Affairs Council, said China not Taiwan was the "troublemaker".
"Over the past six years, we have tried to maintain the status quo of the Taiwan Strait, but China has kept stepping up its arms build-up," he said.