SYDNEY (Reuters) - Australian consumer sentiment took a step back in December as concerns about the economic outlook outweighed an improvement in people's own finances, a survey showed on Tuesday.

The Westpac-Melbourne Institute index of consumer sentiment fell 2.0% in December, unwinding a little of the sharp gains seen over the previous two months. The index is still up 13% on a year ago but at 92.8 showed pessimists again outnumbered optimists.

Westpac Senior Economist Matthew Hassan said the pullback was likely influenced by a disappointing reading on economic growth released in early December.

As a result, the index measuring the economic outlook for the next 12 months slid 9.6% and the outlook for the next five years dropped 7.9%.

In contrast, the measure of family finances compared to a year ago rose 6.9%, still benefiting from tax cuts introduced from July.

The biggest decline came in those with mortgages, reflecting doubts about when borrowing rates might finally fall.

The Reserve Bank of Australia kept interest rates unchanged at 4.35% all year, though it did soften its tone this month and opened the door to easing as early as February.

There was some improvement in the "time to buy a major household item", which firmed 4.8% but remains below the 100 break-even mark.

A separate survey from ANZ showed its confidence index fell 1.6% last week, largely due to a sharp drop in shopping intentions following Black Friday sales.

Westpac's time to buy a dwelling index fell 6.0% in December to a pessimistic 81.6, reflecting high mortgage rates and a lack of affordability.