Taiwan's President Chen Shui-bian has accused Beijing of trying to interfere in elections to choose a new National Assembly, due to be held on Saturday.
James Soong's trip to Beijing follows shortly after a trip by Lien Chan
Mr Chen said Beijing was trying to seek the support of Taiwanese opposition parties against his reform proposals.
These proposals include authorising the use of referendums for future changes to Taiwan's constitution.
Mr Chen's comments came as a Taiwanese opposition leader, James Soong, continued his visit to the mainland.
Mr Soong's visit follows soon after that of another opposition leader, Lien Chan.
Taiwan's President Chen Shui-bian had given both trips his blessing.
But despite being the island's leader, Mr Chen himself is unlikely to receive such an invitation.
Beijing refuses to talk to Mr Chen until he accepts its one-China policy - acknowledging Taiwan is a part of China.
China has certainly rolled out the red carpet for Taiwan's opposition leaders, according to the BBC Taiwan correspondent Chris Hogg.
In recent days, Nationalist Party leader Lien Chan and James Soong, chairman of the People First Party (PFP), have both been feted by the Chinese leadership.
But in a set-piece television interview on Monday, Mr Chen accused the Communist leadership in Beijing of using the visits to try get involved in Taiwan's domestic affairs.
They are trying "to direct the chess game", he said.
On Saturday, Taiwan goes to the polls to elect a National Assembly.
China says its conservation measures are bearing fruit
This body will be asked to pass controversial constitutional amendments, including a proposal to hold public referendums to change the constitution still further.
President Chen insists the amendments are needed to streamline the island's system of government.
But Beijing fears the measures will be another step towards independence for an island it regards as nothing more than a breakaway province.
A spokesman for the PFP denied that his party's unwillingness to accept the changes had been influenced by his leader's trip to China.
Lee Yung-ping told the Associated Press news agency that the party had long opposed constitutional reform.
During Mr Lien's meeting with Chinese President Hu Jintao earlier this month - the first between Nationalist and Communist Party leaders since the Nationalists fled to Taiwan after losing China's civil war in 1949 - the two men agreed to reduce cross-strait tension.
Mr Soong's visit is continuing in a similar vein.
"Taiwan independence will bring war and disaster," Mr Soong told a group of Taiwanese business executives on Sunday. "We want factories and markets, not battlefields."
Mr Soong spent Monday visiting Juyucun in Hunan Province, the town where he was born. Large crowds welcomed his arrival.
He is also due to hold talks with Mr Hu, in a meeting scheduled for Thursday.
But according to the South China Morning Post, Mr Soong's trip has not been completely to Beijing's liking.
He apparently made reference to the "Republic of China" in a speech at the mausoleum of Emperor Huangdi on Friday, prompting Chinese TV (CCTV) to suspend its live broadcast of a subsequent visit.
Beijing objects to the term "Republic of China" because it is seen to imply that Taiwan is an independent nation.
In contrast, all major events attended by Mr Lien were broadcast live.