A Sinhalese deportee, who said he was tortured on his return to Sri Lanka, was denied an interview with Australian police who were in Colombo, according to a cable released under a Freedom of Information law request by The Guardian.

The police declined the opportunity to interview the man, to avoid interfering with any ongoing Sri Lankan investigation.

A letter by the asylum seeker’s lawyer alleged severe torture, and the cable made clear that the Australian High Commissioner in Colombo was aware of the claims.

Greens senator Lee Rhiannon said the case showed how Australia is continuing to ignore evidence of human rights abuses on the island.

“Time again we have seen that Australian officials are prepared to disregard evidence of torture by Sri Lankan officials that have been exposed by human rights organisations and the media, because it suits their domestic policy,” she said.

“This is a tragic response to very serious and continuing human rights abuses in Sri Lanka that are a result of Australia’s domestic immigration policy.”

Emily Howie, director of advocacy and research at the Human Rights Law Centre, said the monitoring of refugees by Australia was “woefully inadequate”.

“If this is how Australia investigates complaints of severe torture how can we accept government claims that Sri Lankan returnees are not at risk of harm?” she said.

“This kind of monitoring of returnees is woefully inadequate considering the gravity of the complaints made. It is difficult to accept government assertions that Sri Lankans are not harmed on return if an Australian official fails to take the most basic step to look into allegations of extremely serious abuse.”