The Electrical Trades Union has snubbed Labor at its National Officers conference this week, asking a federal Greens MP to open the event for the first time.

Greens Treasury spokesman Adam Bandt will be guest speaker on the first day of the ETU's two-day conference in Adelaide, starting on Tuesday. No one from the federal Labor Party has been invited to speak on either day.

The Greens are on the attack in Melbourne Ports, angry with Labor MP Michael Danby for saying he wants to preference the Liberals ahead of the Greens. Credit:Andrew Meares

It is the first time a Greens MP has been invited to speak at the event and comes after the ETU's fierce campaign against the China-Australia Free Trade Agreement was overrun by Labor's support for the deal.

Mr Bandt will use the opportunity to preview details of the Greens' new energy policy, which will be released this Sunday.