CANBERRA (Reuters) - Global media mogul Rupert Murdoch has waded into Australia's election race, calling a key ruling party platform unaffordable and drawing accusations from Prime Minister Kevin Rudd that he was trying to oust his struggling government.

Murdoch, whose News Corp controls about 70 percent of Australia's newspaper market, questioned in a Twitter message how an ambitious $34 billion super broadband being built by Rudd's Labor was affordable in a slowing economy.

"Oz politics! We all like ideal of NBN, especially perfect for Foxtel. But first how can it be financed in present situation?" tweeted the Australian-born Murdoch, whose global media empire is now based in the United States.

NBN is the national broadband network, a plan to provide an internet connection to every home. But the opposition has promised to spend less on the network and scale back its capability, reflecting tighter financial conditions with economic growth forecast to slow to 2.5 percent this fiscal year.

Murdoch, who owns 50 percent of pay-TV operator Foxtel, was strongly criticised on the opening day of the election campaign on Monday when his best-selling Daily Telegraph newspaper ran a front-page headline "Kick This Mob Out" over a picture of Rudd.

Rudd, who has claimed underdog status ahead of a September 7 general election, told reporters on Tuesday there was no doubt the Australia-born Murdoch was determined to engineer election defeat for Labor after six years in power.

"I think he's made it fairly clear ... that he doesn't really like us, and would like to give us the old heave-ho," said Rudd, whose minority government trails the conservative opposition 48 percent to 52 percent in the latest opinion polls.

Rudd said Murdoch's views on the election campaign largely mirrored those of conservative opposition leader Tony Abbott, who has promised to downsize the planned broadband network.

"Does he sense it represents a commercial challenge to Foxtel, to the major cash-cow for his company, or not?" asked Rudd, referring to the planned broadband network.

"It's a free country, he's entitled to those views. I'm sure he sees it with crystal clear clarity all the way from the United States."

But Rudd denied his criticism hinted at plans to challenge Murdoch's domination of Australia's newspaper market should Labor be returned to power, by changing media laws.

"We have no such plans at all, because we assume that all independent players in the Australian media market will participate within the law, exercise their freedom of speech, as Mr Murdoch is consistently doing," he said.

Labor in March dropped plans to reform media laws and strengthen scrutiny of newspapers and media mergers after phone-hacking scandals in Britain, criticised by the Australian arm News Corp as Stalinist and draconian.

The Labor government and conservative opposition have vastly differing plans for the A$37.4 billion ($34.2 billion) National Broadband Network (NBN), potentially hurting some business stakeholders and opening the door to others, including China's Huawei Technologies Co Ltd.

(Reporting by Rob Taylor; Editing by Robert Birsel)