Indian spies were kicked out of Australia after being caught trying to steal secrets about sensitive defence projects and airport security, as well as classified information on Australia's trade relationships.

The so-called foreign "nest of spies" disrupted by the Australian Security Intelligence Organisation (ASIO) in 2020 was also accused of closely monitoring Indians living here and developing close relationships with current and former politicians.

ASIO Director-General Mike Burgess first alluded to the spy ring in his annual threat assessment delivered in 2021, but, he did not disclose which country was behind the activity, saying to do so would be an "unnecessary distraction".

"The spies developed targeted relationships with current and former politicians, a foreign embassy and a state police service," Mr Burgess said during his March 2021 speech inside ASIO's Canberra headquarters.

"They monitored their country's diaspora community. They tried to obtain classified information about Australia's trade relationships.

"They asked a public servant to provide information on security protocols at a major airport."

Mr Burgess also detailed how the "nest of spies" had successfully cultivated and recruited an Australian government security clearance holder who had access to "sensitive details of defence technology".

National security and government figures have now confirmed to the ABC that India's foreign intelligence service was responsible for the "nest of spies", and "a number" of Indian officials were later removed from Australia by the Morrison government.

The Washington Post this week also reported that two members of the Indian intelligence agency known as the "Research and Analysis Wing" (RAW) were expelled from Australia in 2020 following an ASIO counter-intelligence operation.

Details of New Delhi's clandestine operations in Australia have emerged as western allies grow increasingly alarmed over the actions of Prime Minister Narendra Modi's government across the globe, including an assassination in Canada last September.

In an interview with the ABC while visiting the United States in November, Mr Burgess declined to say whether the Indian government's foreign operations had caused any concern for ASIO back in Australia.

"I don't comment on any actions of any government, and you shouldn't read anything into that, I can assure you though if we saw acts of foreign interference or plotting for that, we will deal with it," Mr Burgess told the ABC.

Further pressed on whether he had ever been involved in the expulsion of Indian personnel from Australia, the ASIO director-general again declined to comment.

"We don't comment on specific operational matters but of course, from time-to-time ASIO will discover undeclared intelligence officers who are operating in our country and through our own actions or asking government to help, people can and do leave this country as a result of being found out."

India is a member of the Quadrilateral Security Dialogue alongside the United States, Japan and Australia, and is considered a crucial defence partner in the Indo-Pacific where concerns over China's military build-up are growing.

In 2022, when delivering his next Annual Threat Assessment, Mr Burgess described how nations that were considered friendly were still trying to conduct espionage against Australia.

"Multiple countries are seeking to conduct espionage against us — and not just those countries that might be considered our traditional adversaries," he then said.