© Ian Waldie/Bloomberg
U.S. President Barack Obama gestures as he speaks during a news conference at the Group of 20 summit in Brisbane, Australia, Nov. 16, 2014.

Australia’s immigration department implemented a new email policy just weeks ago after learning the Guardian was aware of an embarrassing blunder that saw the personal details of world leaders exposed.

On Monday the Guardian reported an employee of the department had inadvertently disclosed the passport numbers, visa details and other personal identifiers of the world leaders attending the G20 summit in Brisbane after an email was mistakenly sent to an organiser of the Asian Cup football tournament because of an autocomplete function.

Related: Personal details of world leaders accidentally revealed by G20 organisers

World leaders including US president Barack Obama, Russian president Vladimir Putin, Indian prime minister Narendra Modi and German chancellor Angela Merkel were among those affected by the breach.

Some of the leaders are beginning to make inquiries about the disclosure, and the White House confirmed the US administration was examining reports of the disclosure of president Barack Obama’s personal details.

Australia’s immigration department has been in damage control mode since the breach was revealed on Monday.

The department took the unusual step of putting up its chief information officer, Matthew Yannopoulos, to explain the breach. He told the Australian the department had now disabled the autocomplete function on emails to prevent a similar breach occurring.

“If you have emailed a person before, you have to retype in their address completely,” he said. “I have made the addressing torturous, so that you actually ­really need to think about it. They are pretty unhappy about it.

“I think we are worried about the importance of the information that we hold, and whilst it is causing a productivity impact on all staff, it is reminding all staff of the criticality of information, because they know why they have done it.”

But the Guardian has learned this policy was implemented just weeks ago, after the department became aware of the Guardian’s freedom of information request for the G20 data breach documents.

The immigration department has not yet responded to queries about why the change was only implemented at this time, rather than when the breach occurred.

The White House deputy press secretary, Eric Schultz, said on Monday the administration was “looking into [the reports] and we’ll take all appropriate steps necessary to ensure the privacy and security of the president’s personal information”.

A senior official in the Indian government told the Hindustan Times: “We have seen the report and will take necessary action at our end on the matter.”

The immigration department also initially determined it was not necessary to inform the world leaders of the breach.

In emails obtained under Australia’s freedom of information laws an immigration department wrote to Australia’s privacy commissioner after the breach and said: “Given that the risks of the breach are considered very low and the actions that have been taken to limit the further distribution of the email, I do not consider it necessary to notify the clients of the breach.”

The office of the German chancellor, Angela Merkel, has also confirmed to Der Spiegel it was not informed of the breach.

“The German government learned about what happened from the press,” a spokesman told Spiegel Online. “The government has none of its own information about this.”