A Stormont deal is possible but must not be “cobbled together”, Sinn Féin’s northern leader has said.

Speaking at this week’s Conservative Party conference, Michelle O’Neill added that any deal must be “rights-based”.

This fits in with what Sinn Féin has been saying since it pulled Stormont down 10 months ago: that there is no point putting it back up again unless the DUP’s “battle a day” attitude is replaced with a new, co-operative approach.

Steven Agnew, leader of the Greens in Northern Ireland, thinks this is a duplicitous posture. Speaking at his party’s conference last weekend, he accused Sinn Féin of not wanting a new approach.

Unionists are now a minority at Stormont, Agnew explained, so they depend on the assembly’s elaborate cross-community veto mechanism – the petition of concern – to block the policies Sinn Féin is seeking.

A majority of Assembly members are in favour of same-sex marriage and an Irish-language act.

Yet Sinn Féin has shown no interest in reforming the petition of concern, although that is the simplest, most obvious and only sustainable way to create the new system of “progressive” politics it claims to want.

This is an active omission because reform of the veto was agreed at the 2015 Fresh Start talks, then promptly forgotten, making it a glaring absence from Sinn Féin’s proclaimed agenda of allegedly unmet commitments.

The Green leader’s speech followed a week of media comment on the continued need for powersharing. As the nationalist minority no longer needs protection from a unionist majority, why must the largest party from both sides always be in government?

For Agnew this is about cynicism. He accused Sinn Féin of wanting to keep Stormont in chaos and not wanting to stop unionists from embarrassing themselves before British and Irish liberal opinion.

The leverage and the glory

A kinder explanation might be managerialism. Why would Sinn Féin, or the DUP for that matter, work themselves out a of job?

Resolving their disputes through a mere rule change would deprive Stormont’s two largest parties of leverage, attention, glory and everything else that makes political life worth living. Worse still, the credit for every “progressive” vote would go to the centrist swing bloc of Alliance and Greens.

This is what happens at Belfast City Council, where Alliance has held the balance of power for 20 years.

Unionists were happy enough with this when they saw Alliance as light orange. Former DUP leader Peter Robinson often cited the council as an effective elected chamber without powersharing.

Since 2012, when Alliance sided with Sinn Féin against flying the union flag from city hall, unionists have increasingly portrayed it as the enemy, while Sinn Féin has not gained much of an ally.

Last month Alliance took the credit for the council’s appointment of an Irish-language officer – a Sinn Féin policy – foreshadowing how this key issue might play out at Stormont.

But Belfast City Council is not a precise analogy of Stormont. It has the equivalent of an assembly but lacks a comparable executive.

Stormont will probably always benefit from powersharing at executive level and there is no reason why unionism’s loss of majority should change this.

Consocialisation, the model of powersharing used in the Belfast Agreement, takes its inspiration from the Netherlands, where it evolved to build consensus in a political system composed entirely of minorities.

What has become redundant at Stormont is not powersharing but vetoes – the petition of concern at Assembly level and the ability of either main party to bring government down at executive level.

These vetoes were very much intended as protections from majoritarianism in a Northern Irish context. In a new era without majorities, all they do is let both sides block each other, frustrating any possible consensus.

A veto to scrapping the veto

Abolishing the veto at executive level might seem too close to abolishing powersharing; under present circumstances it would mean Sinn Féin had resigned to leave the DUP governing alone.

It is not quite that stark, however. In 2008 Sinn Féin boycotted the executive for six months in a row over policing and justice without formally walking away.

Government was semi-paralysed and the DUP was greatly annoyed, but Stormont endured and compromise was reached.

At Assembly level, reforming the petition of concern has been discussed for years, mainly in terms of weighted majority voting.

It takes 30 assembly members to raise a petition, initiating a 60 per cent weighted majority vote, requiring at least 40 per cent on each side.

The DUP, among others, has previously suggested tweaking this to a 70 per cent weighted majority requiring 50 per cent on each side, for example.

Such refinements are now unnecessary. In an Assembly of minorities, a straight 50 per cent is a weighted majority and the entire petition mechanism could simply be abolished.

The real problem is how these vetoes will ever be scrapped while Sinn Féin and the DUP have a veto on it.