ALP sources say Victorian Socialist Left faction secretary Andrew Giles has been sounded out for the vacant federal seat of Melbourne, after finance minister Lindsay Tanner announced to parliament that he would stand down this afternoon.

Crikey understands that powerbrokers inside Victorian branch are keen to swiftly secure a replacement for Tanner, whose resignation came as shock to party insiders.

The Socialist Left has a stranglehold on Tanner’s seat, controlling 11 of its 15 delegates to state conference. Insiders say that there is little standing in the way of Giles in terms of internal opposition.

At this stage, the only possible challenger is senior ACTU industrial officer Cath Bowtell, with some union sources suggesting she could have a claim to the seat as a compromise for missing out on the ACTU presidency. Bowtell is believed to reside in the Melbourne electorate.

Giles, who has been next in line for the inner city seat for several years, would face fierce competition from Greens candidate Adam Bandt, an increasingly visible presence around the electorate in recent weeks. The ALP currently holds the seat by just 4.7%, with a favourable redistribution unlikely to be complete before the election.

Support for the ALP in Melbourne has increasingly rested on Tanner’s broad shoulders, with his personal appeal likely to be worth around 3-4% at the ballot box.

Giles is the current chief-of-staff to Victorian Minister for Community Development Lily D’Ambrosio and formerly served as acting chief-of-staff in the office of Gavin Jennings. He was also a lawyer at Labor-aligned firm Holding Redlich.

Giles was a key player in the Tampa incident, acting for Liberty Victoria on behalf of stranded refugees as a solicitor.

In his resignation speech Tanner said that he had “no future employment” but was keen to secure a post-politics role in either business or academia.

“I feel as if I have walked in the footsteps of giants. It has been an extraordinary privilege and an extraordinary experience that I will remember.

“I am conscious that there will be a number of people in community who will feel let down by my choice.

“A lot of people have invested in me over the years…to those who feel let down, I apologise.

“I remind everyone in the Labor caucus that there is only one reason why any of us are here…the ALP,” Tanner said.