The leak of top-secret Asio advice to the media concerning Scott Morrison’s proposal to relocate the Australian embassy in Israel from Tel Aviv to Jerusalem has been referred to the federal police.

In a bulletin leaked to the Guardian Australia, Asio had warned the move may “provoke protest, unrest and possibly some violence in Gaza and the West Bank”.

The bulletin, marked secret, AUSTEO (Australian eyes only), circulated on 15 October – the day before Morrison’s announcement on the Israel embassy – notes that the putative shift would “attract international attention”.

The director general of Asio, Duncan Lewis, told a Senate estimates hearing on Monday that an internal investigation into the leak was under way and the matter had been referred to the federal police. The advice was not intended to be made public, he said.

“It’s very unusual,” Lewis told the hearing.

He was unable to shed light on how it was leaked but said the bulletins were “widely distributed” across the federal government, state and territory governments as well as various departments and agencies.

“It was a routine piece of advice,” Lewis said, adding that Asio issued multiple bulletins and threat level assessments each week, sometimes every day.

Lewis said Morrison had not sought Asio’s advice on the possible embassy relocation.

“We act on our own volition around these sort of issues, as events develop,” Lewis said. “If there is movement in the policy world, if I judge or the organisation I run judges there are security implications as a result of that policy, then we will produce whatever alerts or warnings that we need.”

The Department of Foreign Affairs and Trade had informed Asio of the pending announcement.

The spy agency wouldn’t usually be consulted on foreign policy developments, he said.

“It is not a requirement it is not something that happens all the time,” he said.

Lewis emphasised there was no specific information there would be violent protests in Australia, following the announcement.

Morrison last Tuesday flagged that Australia might follow Donald Trump’s controversial policy and move Australia’s embassy to Jerusalem – an announcement senior figures conceded was timed to coincide with the Wentworth byelection last Saturday, which the Liberals were at risk of losing.

The high-profile independent Kerryn Phelps remains more than 1,600 votes ahead of the Liberal candidate, David Sharma, as counting continues.

The electorate, held previously by the former prime minister Malcolm Turnbull, is home to a significant Jewish population.

The Coalition considered the implications of Trump’s hawkish position on Jerusalem when Turnbull was prime minister, and dismissed the idea of Australia following suit because of a judgment that it would harm the bilateral relationship with Indonesia.