Tensions within Victoria's Labor government were exposed during the late-night debate when an expletive-laden text message was accidentally sent out.

Health Minister Jill Hennessy called Deputy Premier James Merlino a "c---" in a text message sent to him by mistake on Wednesday night, it has been confirmed by numerous parliamentary sources.

Health Minister Jill Hennessy accidentally sent an expletive in a text to Deputy Premier James Merlino. Credit:Jason South

Mr Merlino, a fierce opponent of the Daniel Andrews government's bid to legalise a strictly monitored euthanasia scheme, had proposed an amendment that would have killed off the bill, long-championed by Labor as a flagship policy.

The amendment was narrowly defeated and it's understood Mr Merlino is angry about the text message from his colleague.