The former Labor leader, 52, was admitted to hospital in Brisbane after suffering acute abdominal pain, a spokesman said.

"Mr. Rudd will have an operation to remove his gallbladder later today," the spokesman said in a statement.

Rudd, who is standing for re-election in his Queensland seat in August 21 national polls, has haunted the election campaign of Prime Minister Julia Gillard, who wrested power from him in a party coup in late June.

Gillard has publicly promised Rudd a senior ministerial role if Labor is re-elected, but her campaign has lost momentum amid damaging cabinet leaks which some have suggested may have come from Rudd.