SYDNEY, Dec 1 (Reuters) - Australian pension funds called on Friday for the government to enact reforms that would make it easier to invest in domestic renewable energy projects and warned that without action investors would opt for more compelling overseas projects.

Australia's electricity transmission network, batteries and sustainable aviation fuel are three areas where simplified planning, subsidised finance and other regulatory changes could catalyse investment, according to a report released by eight major pension funds.

Changes could quickly unlock A$4 billion ($2.7 billion) worth of investment in batteries, the report said.

"The challenge we face is not a lack of capital, but a shortage of good quality investment opportunities," Paul Schroder, CEO of the A$300 billion AustralianSuper, said in a joint statement.

"Collaboration across all sectors of the economy, underpinned by policy certainty, will deliver the outcomes we need to respond to this challenge."

Together, the eight funds manage some A$1 trillion.

Once passive managers who predominantly invested at home, Australian pension funds have become international heavyweights, managing A$2.4 trillion - the fourth largest pool of retirement savings by country globally.

The report noted that a raft of clean energy incentives announced in the U.S., EU, Korea and Canada has sparked global competition for capital

The $143 billion IFM Investors, owned by Australian pension funds and an author of Friday's report, signed a A$20 billion investment deal with the UK on Tuesday. Australian pension fund Aware Super committed A$10 billion.

"Capital will naturally be directed to regions with the most attractive policy settings for investment," IFM Investors CEO David Neal said in the joint statement.

"This blueprint sets out a path to help ensure the growth of industry super funds is harnessed for Australia, as the transition to net zero continues to ramp up globally.”

Australia's centre-left Labor government, which has deep ties to the industry via union-linked "industry funds", has sought to direct more of the country's retirement savings pool to domestic priorities like renewable energy and social housing. ($1 = 1.5110 Australian dollars) (Reporting by Lewis Jackson; Editing by Edwina Gibbs)