Australia's deputy prime minister has announced he plans to retire, with the prime minister likely to announce a cabinet reshuffle before elections due this year.

Deputy Prime Minister Warren Truss, who is minister for regional development and infrastructure, told Parliament on Thursday he will retire at the next election.

Truss also resigned as leader of The Nationals party, the government's junior coalition partner. His replacement as party leader will be decided by his party colleagues later Thursday and the new leader will automatically become deputy prime minister.

Trade and Investment Minister Andrew Robb announced on Wednesday that he too will leave politics at the next election.

Prime Minister Malcolm Turnbull made a major overhaul of the conservative government's Cabinet in September.