A wiretapping network run by Chongqing officials was detected on a phone call made to Chinese President Hu Jintao in August, a discovery that helped topple the city's ambitious party chief Bo Xilai, the New York Times reported.

The Times report said nearly a dozen sources with Communist Party ties had confirmed the wiretapping and the widespread bugging program.

The Party's official version of events has omitted the tapped call by a visiting Chinese minister to Hu in August. If true, the report confirms rumors of the incident that had spread since Bo's ouster in March.

The public case has focused on the suspicious death of British businessman Neil Heywood in November, and his alleged murder by Bo's wife, Gu Kailai, a crime that has upset China's carefully managed leadership transition.

"But the hidden wiretapping, previously alluded to only in internal Communist Party accounts of the scandal, appears to have provided another compelling reason for party leaders to turn on Mr. Bo," the Times said.

There are varied versions of the rumors about alleged bugging by Bo, some of which have been reported by Chinese-language media in Hong Kong and abroad.

The report confirms earlier reporting by Reuters on the widespread, sophisticated bugging network in Chongqing set up by Bo and his former police chief Wang Lijun, as well as rumors about the tapped phone call made by visiting anti-corruption official, Minister of Supervision Ma Wen to Hu.

SECRET INVESTIGATIONS

Sources have also told Reuters the monitoring apparently helped Bo and Wang frustrate secretive investigations by central authorities, including a later visit by discipline inspection officials in January.

The Times quoted party insiders as saying the wiretapping was seen as a direct challenge to central authorities and just how far Bo, now sacked and under probe for disciplinary violations, was willing to go in his efforts to grasp power.

"Everyone across China is improving their systems for the purposes of maintaining stability," it quoted one official with a central government media outlet, referring to surveillance tactics, as saying.

"But not everyone dares to monitor party central leaders."

The Times said Ma's high-security land link to Hu from the state guesthouse in Chongqing was monitored on Bo's orders, and the topic of the call was unknown but probably not vital.

Bo had protected himself and Wang Lijun by explaining away the apparent bugging of the phone call between Ma and Hu as an accident, claiming that Chongqing's bugging equipment would sometimes latch onto calls not meant to be monitored, a source in Chongqing who often mixes with officials told Reuters.

It is unclear why the central authorities did not move to act more quickly against Bo, who as late as January appeared determined to win a place in the Politburo Standing Committee, the party's topmost decision-making council, and to enjoy the support of some senior officials, including domestic security chief, Zhou Yongkang.

"The story about Ma Wen could be true but it also raises questions. It's very serious, so why wait?" a source inBeijing who knows Bo and other senior officials told Reuters.

"Wherever Bo Xilai was posted, he never got along with his superiors," the source said. "That was true when he was mayor of Dalian, in Liaoning, in the Ministry of Commerce. He was always suspicious of his superiors."