Labor frontbencher Joel Fitzgibbon has boldly declared "We won't lose Longman" as his party prepares for an upcoming by-election.
The ALP's Susan Lamb is fighting to reclaim the Queensland seat after being booted from parliament over her dual citizenship.
Ms Lamb faces a tough contest to regain the Brisbane-based seat, which she won by a margin of just 0.8 per cent in 2016.
"We won't lose Longman," Mr Fitzgibbon told ABC radio on Wednesday evening.
Labor MPs Justine Keay and Josh Wilson, along with Rebekha Sharkie from Centre Alliance, also quit after being stung by the citizenship saga.
Labor frontbencher Tim Hammond has also resigned for family reasons, triggering a total of five by-elections.
Mr Fitzgibbon, the opposition's agriculture spokesman, has been trying to muster support from across parliament to phase out live sheep exports.
He believes Labor was close to marshalling the necessary votes but concedes the spate of resignations has made his task "a whole lot harder".
"We don't want to lose Longman for many reasons, but yeah, we don't want to lose Longman for the purpose of this vote either, of course," Mr Fitzgibbon said.
Meanwhile, cabinet minister Mathias Cormann is preparing this week to front WA Liberal members disappointed by the party's decision not to contest the upcoming Perth by-election.