The Department of Home Affairs on Friday released the next steps in its years-long process to privatise Australia's visa processing system, detailing what would be required of the company involved.

Just two bidders are in the race for the contract, which is expected to require at least $1 billion in investment – one helmed by Scott Briggs, Liberal Party heavyweight and friend to Prime Minister Scott Morrison and former colleague of Immigration Minister David Coleman, and another joint bid from Australia Post and Accenture.

Mr Briggs runs Pacific Blue Capital, which holds 19 per cent of the Australian Visa Processing Consortium, along with Qantas Ventures, PwC and Ellerston Capital.

The bidders will be required to develop a "global digital platform" to process applications for temporary Australian visas, of which there were 9 million in 2017-18. The contract would cover 10 years, with the number of temporary visas expected to rise to 13 million a year in 2028-29.

While the signed contract would be required to protect the $2 billion that pours into government coffers every year from visa application charges, it would allow the company running the system to recoup a service fee on temporary visas of around $35 per visa.

Based on last financial year's intake, the $35 fee would bring in $315 million, and under the predicted 13 million visa applications to be made in 2028-29, revenue would increase to $455 million a year.

The documents show the government doesn't intend to pay for the new program, and that the only source of revenue for the winning bidder would be from the service fee. The government expects the platform to be operational in the first half of 2021, first to be rolled out with one visa, and extending to other visas progressively.

Responses from the bidders for phase one of the project must be received by February 20 next year, before the April budget and predicted announcement of a federal election in May, meaning the decision could be made before the caretaker period begins.

At Senate estimates in October, Home Affairs secretary Michael Pezzullo said public service jobs wouldn't be lost under the plan, and the system needed to be overhauled as its legacy computer systems were struggling to keep up with demand. Around 50 different systems are used in visa processing at the moment.

The government has said it will maintain responsibility for actually making visa decisions, but it was necessary to outsource the IT system that handles the visa application process.

The main public sector union has criticised the plans to privatise the visa system, and the tender process, which began when more than 10 companies were involved in an expressions-of-interest round.

“This is not an open tender, as only two shortlisted companies are in line to be handed our visa processing system," Community and Public Sector Union national secretary Nadine Flood said.

"With phase one of this process closing in just over two months on February 20, it looks like the government is racing to sell out our visa processing system before voters can have a say on their plan. Such an incredibly important decision should not be rushed through in the shadows of an election.”

The union is concerned for public sector jobs under the plan as well as costs to those seeking visas.

"This government seems unmoved by the 3000 jobs that are at risk under its plan, and completely oblivious to the disastrous experience of other countries that have already gone down the visa privatisation path," Ms Flood said.

"Ordinary Australians will bear the brunt if it’s allowed to proceed, particularly those who were born overseas. Visas are already far from cheap here in Australia and costs have risen rapidly in the UK in just a few years since visa processing was privatised there."

Correction: An earlier version of this story had incorrect numbers. It has been updated to say the $35 fee would bring in $315 million, and under the predicted 13 million visa applications to be made in 2028-29, revenue would increase to $455 million a year.