(Corrects lead paragraph to say Wednesday (not Friday))
SYDNEY, May 8 (Reuters) - Australia's leader and his main challenger played it safe in an inconclusive final debate on Wednesday ahead of next week's election, though opposition Leader Bill Shorten won momentum with an emotional attack on a newspaper story about his mother.
Polls, which have tightened in recent weeks, show Prime Minister Scott Morrison's centre-right Liberal Party in a losing position. He used the debate to attack Shorten's Labor Party's proposed tax and climate change reforms as too risky and expensive at a delicate moment for the economy.
Shorten countered by saying they were necessary to maintain growth in one of the first discussions of the headwinds facing Australia in a campaign where trade tensions and an increasingly dovish central bank have roiled markets and the currency.
"With a trade war between China and the United States, and all the other uncertainties that are in our region, I believe that what's important for Australians ... is that we ensure that they have as much resources available to them," Morrison said.
He is running on a platform of tax cuts and economic credentials as a former treasurer just as the economy shows signs of beginning to slow. said his opponent was backward-looking in his answers during the debate before journalists at politicians at the National Press Club in Canberra.
"What this government calls a cost, I call the future. What this government calls a cost, I call a transition in our economy to a low-carbon, much more productive economy," he said.
Sydney think tank the Lowy Institute published a poll on Wednesday showing Australians regard climate change as the top challenge to the country's vital interests. on Wednesday Shorten took aim at a story in News Corporation's NWSA.O Daily Telegraph that criticised him for omitting bits of his late mother's life story in a television appearance.
The paper said Shorten risked losing credibility with voters by recounting, to explain his motivation, how his mother sacrificed studying to be a lawyer to earn a living as a teacher, without mentioning she did become a lawyer later in life.
The tabloid and its News Corp stablemates, which dominate the Australian media scene, have been heavily critical of Shorten and Labor over the month-long campaign.
"I'm glad she wasn't here today to read that rubbish," an emotional Shorten told reporters at Nowra, 140 km (90 miles) east of Canberra. He added that she won little work as a lawyer, finding it very tough as an older woman.
She nevertheless wrote a textbook on education and law, he said. "She's brilliant. And that's what drives me."
Analysts said his delivery and passion would resonate with voters. "It kind of worked for him," said Peter Chen, professor of political science at Sydney University.
"It allows him to reach a constituency of older women who totally understand what that narrative is all about."