The Newspoll gives the Coalition 55 per cent of the two-party vote, down one point on the previous poll three weeks ago but enough to win government if an election were to be held today.
Significantly, Ms Gillard's preferred prime minister rating slipped five points to 36 per cent, while Opposition Leader Tony Abbott's rating rose one point to 40 per cent. The proportion of respondents "uncommitted" to either leader rose four points to 24 per cent.
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Labor's primary vote of 31 per cent, against the Coalition's 47 per cent, is a seven-month low.
As speculation of a Kevin Rudd comeback cools, 62 per cent of voters said a change of the Labor leadership to the former prime minister would make "no difference" to their vote.
And a week after the Greens formally cut ties with Labor, the minor party's primary vote rose two points to 11 per cent, although this is within the Newspoll margin of error.
In a bid to reconnect with voters ahead of the September election, Ms Gillard will spend five days next week in the Labor heartland of Western Sydney, home to several marginal ALP seats.
Her visit will start with a speech at the University of Western Sydney on Sunday and Ms Gillard will stay in a Rooty Hill hotel for the week, instead of making the daily commute from Kirribilli House in Sydney city.
Federal cabinet will also meet in the area and Ms Gillard will answer voters' questions in social media forums and visiting communities.
The visit comes at a critical time, after polling by JWS Research earlier this year found Labor faces a 12 per cent swing against it in NSW marginal seats - potentially a loss of 10 seats - making it the most at-risk zone for the government.
Industry Minister Greg Combet said Ms Gillard would be explaining how the government would support jobs.
"Ultimately, that is what matters," Mr Combet told reporters in Adelaide.
Asked about Ms Gillard's trip, Mr Abbott, who visited western Sydney last month, told the prime minister: "Good on you."
"But what western Sydney wants is not a visit. Western Sydney wants a plan," he said in Rockhampton, Queensland.
Nationals Senate leader Barnaby Joyce says it's a desperate gimmick.
"Leave Rooty Hill's RSL to the people who want to put 20 bucks through the pokies," he said.
"She doesn't need to be there."
Labor councillor Leo Kelly, who serves the city of Blacktown in the heart of the western suburbs, said Ms Gillard may have left her visit too late.
"From what I hear generally, it could be - it could be a bit late," he told AAP.
Mr Kelly says residents want to know how federal Labor will address cost-of-living pressures and bolster financial support for education and transport.
Greens leader Christine Milne said the prime minister needed to explain why she was cutting support for single parents, with many moved to lower Newstart benefits.
NSW Labor senator Doug Cameron said the western Sydney visit was crucial.
"We're in a bit of trouble in western Sydney, but we've just got to cut through the nonsense that's been perpetuated by the coalition on a range of our policy issues," he said.
