THE Australian economy faces a pothole in economic growth because non-mining investment is not adequate to fill the gap left by the fast-fading resources investment boom, an independent forecaster warns.

The total value of investment projects across the nation fell by $24.7 billion in the first three months of the year to $928.9 billion, says Deloitte Access Economics in its latest Investment Monitor.



After several years of booming activity, mining investment now stands just 0.8 per cent higher than a year earlier.



"It is difficult to shy away from the conclusion that Australia's high growth component of investment will soon be fading, with little prospect of an equivalent alternate investment driver coming through," Deloitte Access Economics partner David Rumbens says in the report.



"That's a bit like having Usain Bolt lead out your relay team, passing off to Homer Simpson for the second leg."



The value of definite projects - under construction or committed - rose by 1.5 per cent in the March quarter to a total $451.6 billion, the report released today shows.



But the value of planned projects - under consideration or possible - in the forecaster's database dropped 6.2 per cent to $477.3 billion.



Back in December, the forecaster predicted the outlook for mining investment depended on whether the green light was given in 2013 for the top 10 pending projects.



"With a quarter of the year gone, the largest of these - Woodside's $43 billion Browse LNG project - has been shelved, and the remaining nine seem no closer to going ahead," Mr Rumbens said.



Otherwise, large LNG projects continue to dominate the investment program with the value of oil and gas projects under way in excess of $200 billion.

Mr Rumbens believes there is potential growth for infrastructure investment that supports mining production, such as railways, port projects and electricity.



But he thinks other investment is likely to be steady rather than achieving much growth.



He says non-resources manufacturing investment has all but dried up, with little prospect of a resurgence while the high Australian dollar hurts the sector's competitiveness.



Non-residential building projects are also showing little signs of life, with new approvals still below the peak seen prior to the 2008-2009 global financial crisis.



"Low interest rates will provide support but the overall environment for office and retail demand still remains somewhat dour," Mr Rumbens said.