Shorten terrified by Dastyari: PM

Malcolm Turnbull reckons Labor leader Bill Shorten refused to sack Sam Dastyari himself because he was "frozen and terrified" by the embattled senator.

Senator Dastyari's self-inflicted resignation from the opposition frontbench underlined Mr Shorten's failure in leadership, he said.

"Frozen, terrified by this 33-year-old junior senator... the leader of the opposition did not have the courage or the integrity to stand him down himself," the prime minister told reporters on Thursday in the Laotian capital Vientiane, where he is attending the ASEAN summit.

He questioned what Senator Dastyari's "hold" on Mr Shorten was and his command of numbers in the Labor caucus.

"Bereft of a leader, he had to take the sword into his own hands and dispatch himself," the prime minister said.

"It's an indictment of Bill Shorten's lack of leadership, lack of courage."