Lawyers have accused the Abbott government of "shredding the separation of powers" with new anti-terrorism laws it will rush through Parliament by the end of the month.

The Australian Lawyers Alliance and the Law Council have raised concern at the extent of powers that will be conferred on police and national security agents by the Foreign Fighters Bill.

Illustration: Matt Golding.

Barrister Greg Barns, spokesman of the Lawyers Alliance, said parts of the new law were likely to be challenged in the High Court as unconstitutional and would not be tolerated in countries such as the US, United Kingdom and Canada, which have human rights frameworks in place.

He singled out the intention to allow Australian Federal Police officers and the Australian Security Intelligence Organisation to issue "delayed notification" search warrants – allowing agents to break into homes and search but not have to alert the owner for up to six months – and the plan to empower the Attorney-General to strip terrorist suspects of welfare payments.