Australian Prime Minister Malcolm Turnbull insists he has "no complaints" about the Exclusive Brethren, after reports emerged the Christian sect donated to the Liberal Party.

Dozens of members, who aren't allowed to socialise or vote, donated more than A$67,000 to the Liberal Party on the same day in December 2010, Fairfax reports.

Turnbull told reporters in Melbourne religious groups were entitled to donate, while insisting the coalition was being "massively outspent" by Labor.

Meanwhile, Labor is officially launching its campaign, a day after polling showed the party is struggling to win over voters in Liberal-held marginal seats.


Opposition Leader Bill Shorten has ventured to the western Sydney seat of Lindsay for the launch, where he's expected to push Labor's education, health and NBN policies.

But his message could be sidelined by a Newspoll survey of marginal electorates in Queensland, New South Wales, Victoria and Tasmania which show the party is failing to win votes.

However, Labor could make gains in Perth. Shorten's eyebrow-raising comments linking the same-sex marriage plebiscite to the deadly Orlando mass shooting also threaten to overshadow his campaigning 13 days out from the July 2 poll.

Turnbull was also campaigning in Sydney. A Fairfax Ipsos poll released yesterday puts the Coalition slightly behind Labor at 49-51 on a two-party preferred basis.