The government-appointed council for First Nation’s constitutional recognition may not deliver its report before election day if a double dissolution is called for July.

The Referendum Council was appointed last year to “guide a national discussion” on the issue and was co-chaired by Patrick Dodson, whose replacement is expected to be announced within days.

Remaining co-chair of the council Mark Leibler says he still hopes to hand over a report before June and is “cautiously optimistic” of May 2017 referendum.

Opposition leader Bill Shorten has promised to hold the referendum in May, whilst Prime Minister Malcolm Turnbull has not yet made a commitment.