Taiwan's opposition challenger for the presidency has accused intelligence services under the control of incumbent President Ma Ying-jeou of tracking her campaign events for political advantage.

The allegations – unproven and denied by Ma – conjure up memories of Taiwan's one-party past when Ma's party, the Nationalists, used their total control of the state apparatus to persecute opponents.

"Even if the president did not give an order for monitoring, the heads of intelligence were appointed by him, and they could take the elections as a good time to return the favours," the mass-circulation Apple Daily said in an editorial published on Friday.

The 14 January poll pits Ma, 61, against Tsai Ing-wen, 55, of the main opposition Democratic Progressive party. Polls indicate an extremely tight race.

The allegations of intelligence service abuse were first raised last week by Taiwan's Next magazine, which said the National Security Council secretary General Hu Wei-chen instructed justice ministry investigators to monitor Tsai's activities in May after she became a presidential candidate.

Next said the bureau reported back to a Hu subordinate last month with details of Tsai's campaign events and her meetings with political activists, including evaluations of how many votes they were likely to bring to Tsai should they support her.

It said the information was then passed on to Ma.

The magazine published names of 28 justice officials it alleged were involved in monitoring Tsai and printed a purported bureau memorandum with the political evaluations.

Tsai said Next's allegations raised questions about Ma's oft-repeated promise to keep Taiwan's intelligence services out of politics. "In a democratic society, if the president directs the intelligence services to monitor a rival's campaign, that would be a very serious matter," she said.

Ma denied receiving any information on Tsai and insisted he was opposed to using state organs for political purposes. "I detest this kind of snooping and will by no means allow it to happen," he said.

The National Security Council acknowledged last month's meeting with the Investigations Bureau but denied that it received any campaign intelligence from bureau officials, or that any such intelligence was passed to Ma.

The Investigations Bureau said it followed the activities of presidential candidates in line with its mandate to provide them physical protection, but was in no way involved with collecting political intelligence.