A new poll shows Labor still holds a commanding lead over the Coalition, despite Prime Minister Tony Abbott’s approval rating growing to a three month high.

According to a Newspoll published in The Australian, Labor improved its two-party preferred vote by two points to lead the government, 55 to 45 per cent.

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The poll comes 18 months since the Coalition won power in September 2013, when the party led Labor 53.5 to 46.5 per cent.

If an election were held today, Labor would be a clear favourite to win office.

Labor’s primary vote has grown one point since February, and leads the Coalition 39 to 38 per cent.

The Greens were unchanged on 12 per cent.

Mr Abbott’s disapproval rating is down from its record high of 68 per cent in February to 63 per cent, while his approval rating sits at 28 per cent.

Opposition leader Bill Shorten’s approval rating also improved by four points in the past fortnight, up to 39 per cent.

Mr Shorten has led as voters’ preferred prime minister since November, and is ahead of Mr Abbott 44 to 33 per cent in the new poll.

The poll comes as senior government backbencher Arthur Sinodinos, who publicly supported the leadership spill against Mr Abbott last month, claimed MPs were once again rallying behind the prime minister.

Speaking on ABC’s Lateline on Monday night, Mr Sinodinos said the embattled leader should be “given the time” to change things that were of concern to backbenchers and ministers.

“The Prime Minister heeded the message and changed his behaviour. So we’re all getting behind him to make sure that that change works,” Mr Sinodinos said.

The former chief of staff to John Howard said Mr Abbott would, however, continue to be judged on his performance.

“My job is to get behind him and help him improve his performance and make it a sustained improvement should we win the next election.”