Foreign Minister Julie Bishop has told colleagues that Tanya Plibersek has "taken a leaf out of Julia Gillard's playbook" and is engaged in a "campaign" to undermine her leader Bill Shorten.

In an extraordinary address to the Coalition joint parties meeting on Tuesday, Ms Bishop linked Labor's internal ructions over the party's policy on turn-backs of asylum seeker boats with the ALP leadership.

Loyalty in question: Foreign Minister Julie Bishop (left) with Tanya Plibersek. Credit:Alex Ellinghausen

She told colleagues the deputy Labor leader had embarked on a "campaign to undermine Mr Shorten", according to a source at the meeting.