Malcolm Turnbull holds the line on climate policy and marriage equality plebiscite

New prime minister says 'policies will change in the light of changed conditions' as Labor presses him on his support for unpopular measures

Malcolm Turnbull has defended the Coalition's Direct Action climate policy and having a public vote on marriage equality after the next election, as he came under pressure to explain his U-turns on his first day as prime minister.

Turnbull, who was sworn in as Australia's 29th prime minister shortly before parliamentary question time on Tuesday, thanked the person he had ousted, Tony Abbott, for "his leadership and his service over many, many years" and indicated he would announce a new ministry later this week or early next week.