Data retention cost revealed in budget

Telcos will have to wait until May to find out how much the federal government will chip in for the cost of its new mandatory data retention regime.

Parliament has agreed to new laws that require telcos to keep the phone and internet access records of customers for two years so they can be accessed by security and policing agencies.

Attorney-General George Brandis says the government will make a "substantial" contribution to the cost of setting up data retention capabilities, but exactly how much will be determined in the budget process.