A measure of Australian consumer sentiment slipped to its lowest in more than a year in August as worries over family finances swamped increasing optimism about the economic outlook.

The survey of 1,200 people by the Melbourne Institute and Westpac Bank published on Wednesday found consumer sentiment fell 1.2 per cent in August, from July when it edged up 0.4 per cent.

The index reading of 95.5 was 5.5 per cent lower than in August last year, showing pessimists outnumbered optimists, and the lowest since April 2016.

"The index components point to clear pressure on family finances," said Westpac Chief Economist Bill Evans.