Opposition leader Peter Dutton has had a bumpy start to his last week of election campaigning after his bus got stuck on a median strip in Sydney's CBD, blocking traffic in the middle of peak hour.

Labor Senator Kristina Keneally has accused Peter Dutton of cancelling her trip to visit a Tamil family from Biloela who are being detained on Christmas Island.

After a subdued day on the campaign trail, the prime minister and opposition leader have not held back, trading barbs and personal digs.