Taiwan's main opposition claimed Sunday that Beijing was colluding with the country's China-friendly government to ensure its re-election in January polls, triggering a rebuttal from the ruling party.

The Democratic Progressive Party (DPP), less friendly with the mainland than the ruling Kuomintang, said China was actively backing President Ma Ying-Jeou's re-election bid as the parties are locked in a close race ahead of the vote.

"As of now China has adopted five plans to help the Kuomintang, either in public or in secret. There's only one purpose for this, and that is to help Ma Ying-jeou get re-elected," party spokesman Chen Chi-mai told reporters.

Chen said that China had timed trade moves to coincide with the polls, sending dozens of procurement delegations to Taiwan this year to buy billions of US dollars' worth of goods including flat screens, textiles, food and agricultural produce.

"It is part of Beijing's united front tactics, aiming to win over the hearts of Taiwanese people," he said.

A campaign manager for Ma brushed aside the claim, telling AFP: "This is no news at all. The DPP is used to accusing other people without any concrete evidence."

The DPP also said that China planned to help organise flights for Taiwanese businessmen on the mainland to return home to cast their votes, and was issuing threats of punitive measures if they support candidates other than Ma.

It said pro-Ma campaign offices had also been established on the mainland, a rare move in non-democratic China.

The run-up to the 2012 vote has been complicated by the entry of veteran politician James Soong, formerly a senior member of the Kuomintang, who has said he will run as an independent, rivalling Ma and the DPP's Tsai Ing-wen.

China and Taiwan have been governed separately since the end of a civil war in 1949 but Beijing still sees the island as part of its territory awaiting reunification, by force if necessary.

Ties were strained while the DPP was in power but have improved markedly since Ma took office in 2008 and began promoting trade and tourism with the mainland.

Taiwan emerged from authoritarian rule less than a generation ago but is now a vibrant democracy.