Treasurer Chris Bowen says figures released by Treasury showing it expects the numbers of asylum seekers arriving by boat will climb over the next year are simply a precautionary prediction.
An independent assessment of the federal budget says more boat arrivals are expected this year despite Labor's tough new asylum policies.
The Pre-election Economic and Fiscal Outlook shows 15 thousand 600 people are now expected to arrive in 2013/14 - up from the May budget estimate of 13 thousand 200.
Mr Bowen says Labor's tough new policies for dealing with asylum seekers will work but Treasury is just factoring in the worst case scenario.
"Of course it does go to implications of alternative arrivals scenarios that's unsurprising that if arrivals increased firth then costs would increase further," says Mr Bowen.
"Of course the assumption it is based on is the same assumption as at budget time. And as the document itself says we do expect, to quote the document, material deterrent on future arrivals over time."
At-a-glance: PEFO forecasts
-Growth of 2.5 per cent; unemployment rate of 6.25 per cent
-Deficit of $30.1 billion for 2013-14
-Surplus of $4.2 billion in 2016-17
WATCH: State of budget released
