Naomi Long has warned the UK and Irish governments that failing to reform Stormont would be "catastrophic" for the future of devolution.
The Alliance Party leader has written to both governments putting forward proposals to change how Northern Ireland's power-sharing institutions operate and enable their restoration.
She said that without reform, the collapsed Stormont Executive and Assembly would continue to face a "vicious pattern of ransom politics".
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The DUP has blocked the formation of a fully functioning devolved government since elections in May in protest over Brexit's Northern Ireland Protocol.
The party has refused to nominate a Deputy First Minister, meaning a First Minister cannot be appointed to the joint office to form a new Executive.
Stormont power-sharing rules also mean a Speaker cannot be elected to re-establish the Assembly without cross-community support from unionist and nationalist MLAs.
Mrs Long said Stormont was once again "locked into a cycle of crisis and collapse" following the DUP's refusal to support the nomination of a Speaker and Deputy First Minister.
In her letter, she wrote: "Unless we reform the institutions themselves, we will never break this vicious pattern of ransom politics and end for good the institutions being taken hostage by any one party.
"At a minimum, changes need to be made to the process of nominating a First and Deputy First Minister, so if a party is unwilling to nominate, the opportunity passes to the next largest party.
"To facilitate effective government, weighted majority voting should replace parallel consent for 'cross-community' votes in the Assembly. In addition, the use of petitions of concern and for ‘cross-community’ votes within the Executive should be restricted to specified issues, to prevent wider abuse."
Mrs Long said the "case for reform is indisputable and acknowledged by all parties".
"These proposals represent modest changes but will future-proof the institutions, incentivise collaboration between parties, and ensure every MLA is treated equally," she added.
"Rather than focusing on meeting the latest ransom demands of any one party, this is where government needs to focus to end this destructive cycle for good. To fail to do so will be catastrophic for the future of devolution in Northern Ireland."
It comes as the UK government is set to press ahead with a bill to unilaterally scrap parts of the Northern Ireland Protocol, with the legislation scheduled to receive its second reading on Monday.
This will see the House of Commons debate the main principles of the divisive bill overriding the Irish Sea trade deal, and decide whether it can proceed for further consideration.
DUP leader Sir Jeffrey Donaldson, whose party has refused to resume Stormont power-sharing until their concerns over the Protocol have been addressed, hailed the move as "welcome and sensible".
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