CANBERRA—Any former Howard Government ministers wanting to quit politics should do so immediately to save taxpayers' money being wasted on by-elections, Labor says.
The call follows the retirement of former National's leader MP Mark Vaile, the third Howard Government highflyer to quit politics this year.
Mr Vaile said the timing was "economical" because the by-election for his seat of Lyne could coincide with another in Mayo, prompted by former foreign minister Alexander Downer's departure.
Federal Treasurer Wayne Swan today urged all coalition MPs wanting to quit to do so to enable all by-elections to be held on the same day.
"The Liberal Party ought to organise for them (politicians) to all go at once and just save the taxpayer some money," Mr Swan told the Ten Network.
Mr Vaile's departure followed those of Mr Downer and former agriculture minister Peter McGauran.
And there is ongoing speculation that former treasurer Peter Costello and former immigration minister Kevin Andrews are also likely to call it quits.
Labor frontbencher Penny Wong said the opposition had a responsibility to taxpayers to hold the by-elections simultaneously.
"We obviously have a number of by-elections on the book and it's really up to (Opposition Leader) Dr (Brendan) Nelson to try and ensure that the taxpayer is least disadvantaged by this and that the by-elections occur at the same time," Ms Wong told the Nine Network.
But opposition treasury spokesman Malcolm Turnbull said it was a "furphy" to suggest money could be saved.
"Labor claims that having simultaneous by-elections saves money, it is simply not true," Mr Turnbull told ABC Television.
"You don't save any money by having a by-election in two electorates on the same day versus having one on one Saturday and one two weeks later.
"That (statement) is a furphy."
Mr Costello would make a decision about his future in his own time, he said.
Meanwhile, Greens leader Bob Brown today launched a stinging attack on the major parties for "dumping" the voters in Mayo.
Launching the Green's campaign in Mayo, Senator Brown criticised Labor for not running a candidate and the coalition for allowing Mr Downer to "dump" the seat.
"The people of Mayo ... have got a right to feel miffed by both the parties, the coalition for dumping them less than 12 months after an election and Labor for...not giving them an alternative," Senator Brown told reporters.
"I think it shows great weakness from Labor to not be fielding a candidate in this electorate."
The Australian Greens, The Australian Democrats and the Liberal Party will run candidates in the safe Liberal seat.
Labor is yet to decide whether it will run a candidate in the NSW north coast seat of Lyne which has been held by Mr Vaile since 1993.