With highly contested proposals for increased data retention possibly due before federal cabinet today, last night’s discussion in Sydney by two prominent American whistleblowers was a timely reminder of the dangers of giving governments too much power.

US whistleblower Thomas Drake, a former senior employee of the United States National Security Agency, and Edward Snowden’s US defence lawyer Jesselyn Radack were interviewed by ABC broadcaster Quentin Dempster about the threats to privacy arising from increased digital surveillance. During the event, put on by the Walkley Foundation, they also spoke from a personal viewpoint about the pressures whistleblowers confront in revealing what governments are doing in our name.

Drake said that authority’s common excuse for invading citizens’ privacy — “if you have nothing to hide, you have nothing to fear” — is thought to have originated with Nazi propagandist Joseph Goebbels. Radack concurred, saying that anyone intending to give up their right to privacy could hand her their bank account details and email log-ins. “Privacy is part of individual autonomy and sovereignty, something we supposedly value in a democratic society.”

Both spoke about the unprecedented powers given to security agencies in the wake of the September 11 attacks. Locally, Attorney-General George Brandis and Australian Security Intelligence Organisation head David Irvine have already flagged the threat of local terrorism as justification for an extension of their power to access the communications of Australians.

On top of this, Prime Minister Tony Abbott said last week that he might reverse the onus of proof on people coming back from Syria and Iraq — in that they must show that they are not a terrorist in order to be allowed back into the country. Some experts have said privately that this proposal, which contradicts basic legal principles, had been put forward in order to make the data retention laws look reasonable.

Drake said no one was disputing the fact that there were “clear and present threats” to national security. “But you don’t need to wiretap the world to find them.” The irony is that in any number of terrorism instances, the system failed, Radack said, citing as an example the Boston Marathon bombing going ahead despite clear warnings. In addition, the Edward Snowden disclosures showed that out of 54 terrorist events, only one of those might have been able to be thwarted by the use of intelligence. All the other instances, such as the Shoebomber and the Underpants Bomber, were discovered by “very alert passengers rather than security screenings in the US”.

Although both the American and Australian governments claim to be collecting “metadata” — which is the numbers or email addresses you are calling and emailing, not the content of those messages — this is irrelevant, Radack said. “If I call an abortion clinic, suicide prevention line or Alcoholics Anonymous, you have an idea of what I’m calling about.”

Drake, a decorated US air force and navy veteran, was charged in 2011 by the US government for blowing the whistle on massive multibillion-dollar fraud, waste and abuse at the NSA, as well as the widespread violations of the rights of citizens through secret mass surveillance programs. They dropped their case against him the night before it was going to court in exchange for him pleading guilty to one misdemeanor count of exceeding authorised use of a computer.

Last night, Drake said that “the truth-tellers, the whistleblowers and the hacktivists are canaries in the coal mine of democracy. If we do not have rights such as privacy, then citizens are the subjects of the state, not free beings.” Radack agreed, saying that the “American constitution is designed to protect people from their own government. The people are supposed to govern the government, not the other way around.”