Tony Abbott resigned as Prime Minister on Tuesday after losing a party room ballot to Malcolm Turnbull, who challenged him for the leadership on Monday.

Mr Abbott reportedly faxed his resignation to Governor-General Peter Cosgrove after the spill, breaking with tradition by not visiting Yarralumla in person.

The unique resignation was first reported by veteran correspondent Laurie Oakes on Tuesday.

RESIGNED BY FAX: @LaurieOakes reports @TonyAbbottMHR did not go to Government House to tender resignation. He faxed it. — Samantha Maiden (@samanthamaiden) September 15, 2015

The delay in resignation saw Mr Turnbull sworn in at Government House on Tuesday afternoon, causing a short delay to the start of his first Question Time as Prime Minister.