The Liberal senator Ian Macdonald has said Australia was introducing sweeping changes to asylum-seeker processing laws because it did not want to be beholden to the high court.

The comment was made in the course of a Senate inquiry on Friday into the migration and maritime powers amendment, which would make significant changes to the assessment process for asylum seekers to “fast-track” decision making, and would also reintroduce temporary protection visas.

Leading lawyers and human rights experts had earlier warned the changes were likely to cause major delays in courts and increase the risk that legitimate refugees would be returned to their countries of origin.

Macdonald’s admission was made in an exchange with the Migration Institute of Australia member Nicholas Tebbey.

Macdonald asked Tebbey why the government was introducing the legislation. Tebbey said: “Australia doesn’t want to feel like it is beholden to a 1951 convention any longer.”

Macdonald interjected, and told the inquiry: “No, it doesn’t want to be beholden to the high court who will pick every comma in the wrong place to allow someone in.”

“That’s the purpose of it. If what we deal with are refugees who we used to deal with through UNHCR in an ordered way, none of this will be important.”

Legal experts said the bill headed off a number of recent and upcoming high court decisions, including the looming decision regarding the detention of 157 asylum seekers at sea in July.

When the bill was first introduced, Morrison denied it was aimed at targeting adverse decisions from the courts when questioned about the case of the 157 asylum seekers.

“That is a pretty speculative question. We are simply seeking to further strengthen the existing powers that we have,” he said.

Dr Michelle Foster, the director of the international refugee law research programme at Melbourne University, told the committee the new legislation would substantially limit the way the courts could consider treaties that Australia had signed, including the refugee convention.

“Where a piece of legislation references an international treaty … then the courts will give consideration to that international treaty,” she said.

“Once you remove all the references to the refugee convention …the hope is that they won’t refer to international jurisprudence or to the jurisprudence of our own court.”