MALCOLM Turnbull has had his equal best Newspoll result since the 2016 election, strengthening his position as Australia's preferred prime minister.

The poll, published by The Australian on Sunday night, shows the PM has jumped eight points in his approval rating, taking him up to 46 per cent.

Opposition Leader Bill Shorten has fallen by three points to 32 per cent following a citizenship crisis that forced four Labor MPs to resign from parliament.

But the Coalition is still trailing Labor 49-51 on a two-party preferred basis for the second consecutive poll.

That margin is the Coalition's best position since September 2016 as both major parties gear up for a string of by-elections to be held across the country as soon as July.

However, a Fairfax/Ipsos poll shows the government losing ground over the income tax cuts, with Labor's primary vote rising to 37 per cent from 34. There was no change in the Coalition's primary vote at 36 per cent.