Ms Gillard called the ballot for the Prime Ministership after Kevin Rudd held a press conference in Washington this morning to declare he was the best person to lead Labor to an election.

Mr Rudd told journalists he had had ''many encouraging'' discussions with colleagues over night.

Despite declaring he was the best to lead Labor, he stopped short of declaring he would contest the Prime Ministership with Julia Gillard.

The press conference was broadcast on ABC radio this morning, shortly after 9am.

The former Foreign Minister — who resigned from his post yesterday — said he had been ''astonished'' at the character attacks he had heard directed at him by cabinet ministers in Australia.

He went on to say that he was the best leader for Labor to defeat opposition leader Tony Abbott at the next election but did not formally challenge Ms Gillard.

Mr Rudd then outlined what he called his ''achievements'' when he was Prime Minister and gave a broad policy platform that he would pursue if elected Prime Minister.

Ms Gillard held a press conference in Adelaide about 10am, to answer Mr Rudd.

She declared the ballot was on.

‘‘Following on from Kevin Rudd’s resignation . . . I have decided that this is in the interests of the labor Party,’’ she said.

‘‘For far too long we have seen squabbling in Australian politics and Australian’s are rightly sick of this and want it brought to an end.

‘‘I expect to receive the support of my Labor colleagues (at the leadership ballot) . . . but if to my surprise I do not succeed, I will go to the back bench and relinquish my ambitions for leadership.’’

Ms Gillard then said she would expect Mr Rudd to relinquish his ambitions for leadership, if he lost the ballot on Monday.’’

Ms Gillard then went on to outline what she saw as policy reform achievements she had accomplished since being Prime Minister; she listed the successful passing of carbon price legislation through the parliament and the Minerals Resource Rent Tax.