The Labour leadership contender said he wanted a new constitutional set-up 'based on federalism'.
Phillips dropped out of the race to succeed Jeremy Corbyn but is backing the Edinburgh South MP for deputy.
The shadow business secretary says independence would be for the people of Scotland to decide.
Scotland's only Labour MP has launched a bid to become the deputy leader.
The Ross, Skye and Lochaber MP has been unanimously re-appointed at the parliamentary party's AGM.
Boris Johnson's party has cleared the hurdle of seats needed to govern in the Commons alone.
The Labour leader described the general election result as 'very disappointing'.
The SNP are on course to win 55 seats, up 20 and their second best result of all time.
All the main UK-wide parties have now revealed their pitches to voters ahead of December 12.