Australia's election campaign was hijacked on Friday by police raids on the Labor opposition, over a suspected leak of documents citing cost blow-outs in a multibillion-dollar broadband upgrade, sparking concerns about abuse of power.

Labor questioned the timing of the raids and whether the government had put pressure on police, while Prime Minister Malcolm Turnbull and the head of the Australian Federal Police (AFP) rejected any suggestion of political interference.

The controversy capped the second week of campaigning ahead of a national election set for July 2, in which polls indicate a tightly contested race between Labor and Turnbull's Liberal-National coalition government.