In an interview with Italian reporters, Zhu scorned Taiwanese President Chen Shui-bian. He questioned Chen's experience and mandate, since he won the three-way March election with 39 percent of the vote.
"If you say the president there was democratically elected, I believe this is a joke," Zhu said, according to a transcript of an interview Monday that was made public Wednesday by the Italian news agency ANSA.
"In Taiwan, he only got 40 percent of the vote, he has no administrative experience and even they acknowledge that Taiwan engages in 'black-gold politics,' " Zhu said, using a popular Taiwanese phrase for political corruption.
Zhu's harsh rhetoric, while distorting Chen's record, underscores Chinese leaders' misgivings about the Taiwanese leader and their fear that after 51 years of separation the island may be slipping further from Beijing's grasp.
Zhu's comments were released one day after Taiwan's new leader made one of his strongest appeals to China to join him at a summit to discuss disputes that have separated the two sides for five decades.
At his first news conference since his inauguration one month ago, President Chen Shui-bian said that this is an "age of reconciliation" and that the time is right for a first-ever summit between the rivals that split amid civil war in 1949.
"We have a lot of international trends behind us," said Chen.
Chen was mayor of Taipei from 1994 to 1999 and earned praise for trying to end widespread corruption under the ruling Nationalist Party. Chen is with the opposition Democratic Progressive Party.
While his party still champions Taiwan's outright independence from China, Chen was not as vocal about it during the presidential campaign.
He ousted the Nationalists in the election and his inauguration a month ago arguably marked the first democratic transfer of power in 4,000 years of Chinese history.
Chen has made repeated overtures to Beijing, but he has steadfastly refused to yield to Beijing's demands that he acknowledge that Taiwan is a part of China as a condition for talks.
China has tried to pressure Chen into talks by threatening to unify the island by force, while also calling for him to demonstrate his good intentions with deeds.
The government-run Xinhua News Agency suggested Wednesday that Chen's party could ease tensions by ending its formal support for Taiwan independence.
In an editorial, Xinhua said that the Democratic Progressive Party's calls for a vote on establishing a renamed Republic of Taiwan are a "malignant tumor and stumbling block in the improvement of relations between the two sides."
Whether the party scraps the Taiwan independence platform at an upcoming congress is "an indicator of whethr the DPP is sincere about wanting to improve relations between the sides," Xinhua said. "We will wait and see."
Shortly after Chen's election, his party's leaders discussed scrapping the Taiwan independence platform. While few Taiwanese support uniting with the mainland, they fear China would make good on its threat to attack if Taiwan declares independence.
China and Taiwan have allowed family reunions and significant trade between the mainland and Taiwan's free-market economy.
Bowing to demands by businesspeople, Chen has pledged to consider ending a five-decade-long ban on direct shipping and air links with China. But he told reporters that ships and planes will never travel directly between both sides unless leaders can sit down and fix questions about custom regulations and other things.
"These issues call for meetings, negotiations," he said.