Malcolm Turnbull has hinted embattled Labor senator Sam Dastyari could be under security agency investigation as he seeks to ramp up pressure on Bill Shorten to boot him out of Federal Parliament.

The Prime Minister says Senator Dastyari "betrayed Australia" in his dealings with billionaire Chinese donor Huang Xiangmo and the Opposition Leader is "failing as a leader" by sticking by him.

As revealed by Fairfax Media last week, Senator Dastyari warned the Chinese Communist Party-linked Mr Huang his phone was likely being tapped by intelligence agencies, during talks in October last year.

Their meeting in the grounds of Mr Huang's Sydney mansion came two weeks after Senator Dastyari quit the Labor frontbench over his financial dealings with Mr Huang. Before they spoke, Senator Dastyari said they should leave their phones inside and go outside to speak.