Opposition suspicions that Anthony Albanese’s broken tax promise was poll-driven were fuelled by internal Liberal research that showed the prime minister’s support had plummeted in the marginal seat of Dunkley, where voters go to a byelection on March 2.

The polling, to which Opposition Leader Peter Dutton alluded last week when he accused the government of panicking after being abandoned by middle Australia, shows Mr Albanese’s net favourability in Dunkley was minus 11 per cent.