The coalition would lose an election if it were held today, a poll suggests, as voter backlash mounts over the planned new debt tax.

Two party-preferred support for the coalition has plunged 5.5 percentage points since the September election, a Galaxy poll commissioned by News Corp Australia has found.

The coalition sits on 48 per cent, compared to Labor’s 52 per cent.

Voters have abandoned the government, the poll suggests, over its deficit tax plan, with 72 per cent of respondents saying it represents a broken promise.

It’s understood there are rumblings in the cabinet room, with senior Liberals, including deputy Liberal leader Julie Bishop and Communications Minister Malcolm Turnbull, holding reservations about the planned tax.

The coalition’s primary vote has fallen from 45.5 per cent at the election to just 39 per cent now.

Labor, however, is still languishing on 37 per cent, and has not been able to gain traction from the hit to Prime Minister Tony Abbott’s coalition.

The Greens have picked up more than two percentage points, with voters also migrating to independent candidates and other minor parties.

Galaxy has found 65 per cent those polled disagree with the government’s paid maternity leave scheme in the current budgetary environment, News Corp reports.

The prime minister recently announced the wage cap for his signature policy would be reduced to $100,000 a year, from $150,000.

But the national commission of audit, which released its report on Thursday, recommends that should be watered down further to be capped at average annual earnings.

Cabinet will hold talks again on Wednesday and Treasurer Joe Hockey will hand down his first budget on May 13.

The Galaxy poll was taken between April 30 and May 1 and results are based on the opinions of 1391 voters.