"We can't afford to have our nation drift for eight days after an election", the Opposition Leader said.
Australians usually know who their next leader will be on the night of their vote, but the July 2 poll was too close to call, triggering a complicated system of centralized vote counting that still hasn't technically finished.
That prompted opposition leader Bill Shorten to formally concede the race on Sunday, which in turn triggered Turnbull to announce that the coalition had won a second three-year term.
Turnbull thanked Australian people for voting him in.
But Turnbull's party coup replicated similar putsches inside the Labor Party when it was in office before 2013 and meant that Australia had its fifth prime minister since 2007.
The Townsville-based seat of Herbert is still line-ball with Labor ahead by just 302 votes with almost 7000 votes to be counted.
Australia's prime minister has declared a narrow victory on the eighth day of vote counting in marathon federal elections.
It probably wasn't the welcoming note Malcolm Turnbull was hoping for on his first day back as prime minister.
Shorten, who had previously indicated he would not concede until the coalition officially won 76 seats, said he could not be prouder of Labour.
Although he is expected to form a majority government, Turnbull's gamble in calling the election backfired badly, with a swing to the center-left Labor opposition and a rise in the popularity of minor parties and independents.
Parties are required to hold at least 76 seats in the House to form a majority government.
This will be particularly challenging in the Senate, where the Government will have to either do deals with Labor to get legislation passed or win the votes of a bunch of small party senators.
Even if Turnbull manages to cling to power, he faces a slew of new challenges.
Mr Shorten said he had also written to Mr Turnbull to call for a bipartisan investigation into electronic voting because of how long it has taken the Australian Electoral Commission to determine the result.
Despite claiming before the election that no changes to the frontbench would be made, Turnbull will be forced to make some changes due to a number of ministers losing their seat at the election.
Fresh impetus to make budget repairs has come in the form of a warning by Standard and Poor's to place Australia's coveted AAA-rating on negative watch from stable.
In Flynn, which stretches inland from the city of Gladstone, the LNP's Ken O'Dowd trailed his Labor opponent for most of last week but is now ahead by 391 votes with 5,783 left to count.
The prime minister has his party's support for now, but his enemies are watching closely.
'I hope it proves to be a turning point in the approach to economic decision making in our country, ' Mr Pearson told reporters in Canberra on Monday.
"Yes, this is something we must look at", he said. "Those who are in a better position to contribute, including those who are taking advantage of tax concessions, have a role to play in budget fix".