Labor has restored a commanding lead over the Coalition in the latest Newspoll, with the federal opposition holding a 55% to 45% advantage after preferences.

The fortnightly poll, published in The Australian newspaper on Tuesday, also showed the prime minister, Tony Abbott, and the opposition leader, Bill Shorten, both improved their personal approval ratings.

Newspoll’s two-party-preferred figures have bounced around to an extent in the leadup to and aftermath of the failed spill motion against Abbott’s leadership last month, but now appear to be stabilising to the levels recorded late last year.

The Liberal-National Coalition sank to 43% in the poll taken on 6 to 8 February, surged to 47% a fortnight later, and then split the difference to register 45% in the latest survey of 1,161 voters from Friday to Sunday.

The two-point decline in the Coalition’s two-party-preferred rating in the past fortnight followed a one-point increase in Labor’s primary vote to 39% and a one-point drop in support for minor parties and independents to 11%. The Coalition’s primary vote was stable at 38% and support for the Greens remained steady at 12%.

The poll, which had a 3% stated margin of error, showed the percentage of people satisfied with Abbott’s performance increased three points in the last fortnight to 28% and dissatisfaction dropped five points to 63%. This produces a net approval rating for Abbott of minus 35 (an improvement of eight points).

Over the same period, satisfaction with Shorten’s performance rose four points to 39% and dissatisfaction dropped seven points to 42%. Shorten’s net approval rating of minus three represented an improvement of nine points since the previous poll.

Shorten also registered a slight increase in his lead as preferred prime minister. When asked who would make a better prime minister, 44% of people surveyed by Newspoll nominated Shorten while 33% nominated Abbott.

In the past fortnight, Abbott bowed to longstanding internal and external pressure to drop the GP co-payment and to improve the defence force pay deal. He also announced plans to send an extra 300 troops to Iraq on a joint training mission with New Zealand.

The government released the intergenerational report on Thursday, paving the way for debate about how to tackle demographic changes and budget challenges over the next 40 years. It also prompted renewed debate about proposed changes to the rate of increase in the age pension.

Shorten continued his criticism of the government’s “chaos and dysfunction” and unveiled a Labor policy to crack down on multinational tax avoidance.

The Coalition won the 2013 election with a two-party lead of 53.5% to 46.5%.