The cash holdings represented 28 per cent of all SMSF assets, which hit $558.6 billion in the March quarter, up 2 per cent from $547.6 billion in December 2013.

Market Vectors Australia managing director Arian Neiron said these figures may negatively impact SMSFs ability to grow or even protect their wealth.

"Given that inflation could head higher and cash rates could remain steady SMSFs are risking value erosion by being so heavily invested in cash," Mr Neiron said.

"Annual inflation was 2.9 per cent so the real returns on cash investments are close to zero, add in tax and you are in negative territory.”

“The Reserve Bank has this week indicated that it is not likely to raise interest rates anytime soon and banks have lowered rates on term deposits, SMSF investors should consider their options to protect against rising inflation," he added.

Mr Neiron said however that there is one positive aspect of the ATO data, with it revealing cash investments had slowed to 1.6 per cent from 2.1 per cent a year earlier.

“[This highlights] that SMSFs' appetite for cash investments could be waning," he said.