Beijing yesterday stepped up its criticism of Taiwan leader Chen Shui-bian for preaching separatism through a proposed referendum and new "constitution,'' warning such a pro-independence move could spell disaster for the island.

"We respect the wishes of Taiwan compatriots to be their own masters, but firmly oppose any attempt to challenge the one-China principle and split the motherland,'' said Zhang Mingqing, spokesman for the Taiwan Affairs Office of the State Council.

He told a regular press conference that a handful of diehard separatist members led by Chen are using the referendum as a ploy for their splittist conspiracy rather than what they call a promotion of "democracy'' for Taiwan.

Chen has listed introducing referendums and revising the "constitution'' as two of his key campaign promises in a bid to win re-election in next March's "presidential'' polls.

At a mass rally on Saturday in the southern city of Kaohsiung, Chen said the island needs to rewrite its "constitution'' and pass a law allowing referendums if it wants to become "a normal and complete country.''

The leader of the pro-independence Democratic Progressive Party also told his supporters that "Taiwan and China are one country at each side (of the Taiwan Straits),'' which he first advocated in August last year.

Chen's recent schemes are widely believed to be aimed at paving the way for an independence referendum.

Since taking power on May 20, 2000, the Taiwan leader has refused to embrace the one-China principle that states there is only one China consisting of both the mainland and Taiwan.

When he assumed office, Chen committed himself to the "four nos,'' which require Taiwan to refrain from declaring independence; changing the "national title''; including the concept of "state-to-state'' relations between the island and the mainland in its "constitution''; and promoting any referendum on changing the status quo on independence.

But Zhang noted that Chen's intensified advocacy of separatism has proven that his pledge to follow the "four nos'' was nothing but a lie.

Zhang warned that the splittist activities by Taiwan pro-independence elements, which go against the fundamental interests of Taiwan compatriots, will only bring disastrous consequences to the island.

"No form of pro-independence activity can be tolerated by the whole Chinese people and it is doomed to complete failure,'' the spokesman said.

"We stand firm on the issue of safeguarding the sovereignty and territorial integrity of China because it concerns the significant national interests of the entire Chinese nation and allows no ambiguity and concession.''

While promoting peaceful reunification between the Chinese mainland and Taiwan, Beijing does not undertake to denounce the use of force in case of Taiwan declaring independence.

Zhang also cautioned that stopovers in the United States by Chen will damage Sino-US ties and increase cross-Straits tension.

He accused Chen of using the "transit diplomacy'' to engage in inappropriate activities to promote splittist ideas such as "one China, one Taiwan'' and "two Chinas.''

The United States granted Chen permission to stop in New York on October 31 and in Anchorage, Alaska, on November 6 en route to and from Panama, one of a handful of countries which recognizes Taipei.

At yesterday's press briefing, a mainland agricultural scientist also confirmed that crop seeds from Taiwan were aboard the Shenzhou-V manned spacecraft, which returned to the Earth on October 16 following the historic 21-hour space voyage.

The 33 varieties of crop seeds, weighing a total of 100 grams, include flowers and vegetables and were provided by Taiwan counterparts, according to Zhao Linshu, an associate researcher with the Space Breeding Centre under the Chinese Academy of Agricultural Sciences.

She said the co-operation will help boost cross-Straits exchanges in agricultural science and benefit agricultural development on both sides of the Straits.