The headline change to the package is the axing of a proposed $500,000 lifetime non-concessional cap on super, which was to be backdated to 2007.

That backdating to 2007 was condemned by sections of the Coalition base – who rushed to praise the backdown on the cap – and lambasted by Labor for being retrospective.

Labor characterised the decision to drop the $500,000 cap as a "capitulation" after months of "chaos and dysfunction" over the policy but shadow treasurer Chris Bowen would not say whether the opposition would now support the policy, promising only to look constructively at the legislation when it is released in coming months.

Eventually, however, the opposition is expected to adopt the government's super changes.

Earlier this week, the Coalition and Labor struck a deal on the $6.3 billion omnibus savings bill and the long-awaited approval of the package by the Coalition party room opens the way to a deal with Labor and means the government is poised to secure support for a second budget repair measure.

The cap will be replaced by a new measure that reduces the existing annual non-concessional contributions cap from $180,000 per year to $100,000 per year, with a three-year bring-forward, until a balance of $1.6 million is reached.

The redesigned package was ticked off by cabinet on Wednesday night and approved by the Coalition party room on Thursday morning.

Mr Morrison said the changes would make the superannuation package, which raises about $6 billion in revenue and contributes $3 billion net to the budget bottom line "even fairer, even more flexible and even more sustainable".

"These measures remove any remaining impediment or barrier for the government's budget superannuation package to now receive bipartisan support in this Parliament. This morning I've spoken to the shadow treasurer, Mr Bowen, and outlined these measures to him and offered him and his team a full briefing from officials."

"Labor has no excuse whatsoever not to immediately, I would say, subject to their normal processs, support this. It removes every impediment that Labor mentioned ... what this has demonstrated is a government that can deal with tough issues in the 45th Parliament."

During the election campaign, Prime Minister Malcolm Turnbull had described the super package as "ironclad" and Mr Morrison had, similarly, defended the package as set out in the May budget.

Despite the fact that the package has now been changed, Mr Morrison dismissed suggestions the compromise represented a backdown or broken promise, and insisted the $500,000 cap had not been retrospective.

In Question Time, the opposition mocked the government's backdown but Mr Turnbull said that, after consulting the backbench, the opposition and crossbench "we have achieved changes which we believe meet all of the purposes, all of the objectives. They are absolutely consistent with our commitment to ensure that super is fairer, more flexible, achieving Budget savings, operates with greater integrity".

The dumping of the $500,000 cap will cost the budget $400 million but two other changes – a one year delay in the start date for concessional superannuation contributions and dumping a change that would have allowed the harmonisation of contribution rules for those aged 65 to 74 – will save $580 million and offset the cost.

Nationals MP George Christensen, who had threatened to cross the floor and oppose the legislation, rushed to praise the Treasurer, declaring the change had "completely removed any concern that I had about the superannuation reform package".

"The doing away of the $500,000 non-concessional lifetime cap goes even further than I would have thought ... this really does seal the deal and as such, I can say I am 100 per cent supportive of the new superannuation reforms that we will take to Parliament and I will no longer be crossing the floor."

Former cabinet minister Eric Abetz was similarly effusive.

But that praise prompted Mr Bowen to taunt the Treasurer that Mr Christensen was "writing government policy" and on that basis, "we reserve the right to take our time to scrutinise it very carefully".

He pointed out that the government had criticised Labor's call to dump the measure for 65 to 74 year olds, and criticised the one year deferral.

"We will satisfy ourselves it's good policy on behalf of the Labor Party before supplying the Labor Party's votes in the Parliament to pass something, sight unseen," Mr Bowen said.

Industry Super chief executive David Whiteley said the deal should be a "workable compromise" the Parliament could agree to.

"We would hope all MPs will now give careful consideration to these changes so the reforms can start to make their way through the Parliament. These are evolutionary, not revolutionary changes," he said.

Labor will be briefed by Treasury officials in the coming months and the legislation will be released by the end of the year.

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