The Public Sector Superannuation Accumulation Plan, better known as the PSSap, gave members of its standard account a 7.7 per cent return in 2018-19.

The result was the ninth best among about 50 standard, or "balanced", funds in the industry, according to SuperRatings.

By comparison, the average return was 6.9 per cent.

However, the PSSap's best performances were in the "aggressive" and "income-focused" categories - options for members who prefer high and low-risk investments respectively.

The fund's income-focused option - designed for workers near retirement who want to invest safely - was the industry's best in that category, returning 7.6 per cent.

Its aggressive option delivered the industry's second-highest returns for the year, yielding 9.6 per cent.

The PSSap is the default super fund of almost half (48 per cent) of all federal public servants, according to the government's latest pay data.

It was set up after the previous default fund - the PSS - proved too generous and was closed off to new staff in 2005. The PSS itself was set up as a more "financially sustainable" fund when the Commonwealth Superannuation Scheme, or CSS, was closed 15 years earlier.

More than 55,500 public servants are still members of these closed funds - just over 40 per cent of current staff.

Unlike members of the closed schemes, PSSap members' retirement income is not guaranteed. But they receive a far larger employer super contribution - 15.4 per cent of income - than most Australian workers, who receive 9.5 per cent.

Meanwhile, UniSuper's accumulation plan - another fund that covers many Canberra employees - topped the industry for balanced accounts in 2018-19, returning 9.9 per cent.

UniSuper was also one of Australia's best-performing funds over 10 years, averaging returns of 9.6 per cent a year, compared with the PSSap's 8.4 per cent.

The Commonwealth Superannuation Corporation, which manages the PSSap as well as other government funds, said on Tuesday it was pleased with the strong returns.

However, it said it remained focused on providing stable pension income to retired members rather than topping investment performance.

"Australia is moving into a new phase of superannuation, where there are more customers drawing down on their super than those that are contributing," the agency said in a statement.

"Given the purpose of [the corporation's] balanced option, it expects that it will outperform peers in volatile and troubled market environments, as it did in the six months to December 2018, but underperform them when markets are driven by a 'herd mentality' rather than fundamentals."