A decision will be made early next year on who will build Australia's $33 million Do Not Call Register, leaving a couple of months to build it.

About 20 million fixed-line and mobile numbers will be eligible for the electronic register to block nuisance phone calls and internet spam.

Up to one million registrations are expected in the first week of operation.

According to tender documents released last week the service provider will be required to have a database with space for 15 million telephone numbers, with capacity to scale up.

The tender to develop and manage the register was released by the Australian Communications and Media Authority. A spokesman said the winner would be announced early next year.

The Do Not Call Register must be operational no later than next May.

The authority will be responsible for overseeing the register and investigating breaches, but all other development and administrative tasks will be undertaken by the winning bidder.

Once the register is operating, anyone with a home fixed line or mobile number will be able to list their numbers for free if they do not want to receive unsolicited telemarketing calls.

Each number will stay on the register for three years unless removed on request.

It will be illegal, in the absence of consent, for any non-exempt telemarketer in Australia and overseas to contact a number listed in the register.

There are a number of exemptions including charities and registered political parties.

Telemarketers will pay a fee to access the register so they can compare their contact lists with it. The fee will help pay for maintaining the register.

Community concern about the growth in unsolicited marketing calls prompted the Howard Government to plan the register. The Government is also developing national standards for telemarketers.

A draft of the standard is expected to be released for comment next month.

Based on international experience, the authority estimates there could be seven million numbers on the register in the first two years.