Australia's major banks are feeling the squeeze of rising funding costs but refuse to increase mortgage rates until after the federal election.

A Macquarie Equities Research report suggests the banks, which could justify lifting their standard variable lending rates, were disinclined by the political environment.

Australian home loan figures soared by 1.9 per cent during May. The average loan size plunged by 1.3 per cent, but the number of new loans swelled amid elevated interest rates.

The large banks have become a focus of Wayne Swan, who has slammed rate rulings outside of the central bank cycle, or moves higher than the RBA's.

The major players have provisionally agreed to limit rate increases to the RBA's official decisions in the short term. However, they are predicted to move after the election, which could be called as early as this week.

The National Australia Bank could be the first among majors to increase rates after the federal poll, according to Macquarie analyst Michael Wiblin said. This is because its standard variable rate of 7.24 per cent was the lowest by 12 basis points.

"The sensitivity around mortgage repricing over the last six months is due to the election."

Australian banks had not been able to follow the international trend of retail banks, especially in the UK, lifting standard variable rates to absorb higher funding costs, Mr Wiblin said.

NAB had kept the standard variable rate in the market for the past year, according to a bank spokeswoman. "We do not comment on speculation by others about interest rates."