JULIA GILLARD has urged against a ''big Australia'', saying people need to ''stop, take a breath and develop policies'' for a sustainable nation.

The Prime Minister contradicted predecessor Kevin Rudd, who was in favour of population growth, as she signalled a tougher approach yesterday.

''I do not support the idea of a 'big Australia' with arbitrary targets of, say, 'a 40 million-strong Australia' or 'a 36 million-strong Australia','' she said.

''Australia should not hurtle down the track towards a big population. We need to stop, take a breath and develop policies for a sustainable Australia.

''If you spoke to the people of western Sydney, for example, about a 'big Australia', they would laugh at you and ask you a very simple question: 'Where will these 40 million people go?' ''