G. Gordon Liddy, a Nixon operative who engineered the 1972 break-in at the Democratic National Campaign headquarters in the Watergate building in Washington, and served four and a half years in jail for it, said Wednesday that Felt "violated the ethics of the law enforcement profession."

"If he possessed evidence of wrongdoing, he was honor-bound to take that to a grand jury and secure an indictment, not to selectively leak it to a single news source," Liddy, now a popular conservative radio talk show host, told CNN television.

"Deep Throat," named after an emblematic porn film of the time, helped Washington Post reporters Bob Woodward and Carl Bernstein draw connections between the break-in and the White House, eventually leading to Nixon's resignation under threat of impeachment.

Forty Nixon aides were indicted as a result of the break-in in which burglars planted listening devices to spy on the Democrats during an election campaign.

Liddy suggested that Felt had been also aware of information that was damaging to the Democrats but chose to keep that silent about it, indicating he was driven by partisan politics.

Leonard Garment, Nixon's chief legal counsellor from 1969-1973, said he thought Felt kept his role in Watergate secret for 31 years "because he felt that what he had done could well be considered dishonorable."

Garment said the question was "when government persons, having private, secret, confidential information, are justified to become the whistle-blower and defy or ignore their sworn obligation to maintain security and go to the press with it."