The Australian immigration budget has increased by $1.3 billion over four years, as the government prepares to expand the humanitarian visa program to 20,000 each year.

A Senate estimates hearing on Monday was told the Immigration Department's budget for humanitarian arrivals will rise by $150 million this year alone, accounting for about $24,000 for each person resettled in Australia under the expanded humanitarian program.

The government said in October that it would expand the program by 6250 places each year, mainly from source and transit countries. That was as part of its plan to reopen Nauru and Manus Island and keep pushing for the Malaysian plan to stem boat arrivals.

But senators were told that just 675 people had been resettled from Malaysia and 123 from Indonesia under Australia's expanded resettlement plan. This means plans to resettle 1350 people from Malaysia, and 600 from Indonesia, by June 30 will have to be accelerated.

When the government announced its plans for a ''people swap'' with Malaysia, a proposal later struck down by the High Court, the Coalition condemned the deal on the grounds that asylum seekers' human rights would not be protected, pointing to Malaysia's refusal to sign the refugee convention.