Latest: James Brokenshire returns to Stormont to lead talks

Sinn Fein has claimed the DUP are standing in the way of a deal and urged the British and Irish governments to intervene, but a representative of Northern Ireland's main unionist party said he would be happy to nominate devolved ministers on Thursday.

The parties have until 4pm on Thursday to nominate ministers to a new coalition executive or they face the prospect of some version of direct rule to be imposed from Westminster - or yet another snap Assembly election.

Among the sticking points are republican demands for an Irish Language Act which would bestow official protection for the minority tongue and equal rights for the LGBT community.

Senior Sinn Fein negotiator John O'Dowd said: "There is clearly an onus on the governments to inject energy into these talks, to inject leadership into talks and ensure the outstanding issues are resolved in the time-scale we have left to us."

The DUP has told the republican party to stop indulging in "high-wire acts" and get down to the job of delivering for the people.

The DUP is willing to legislate on the language issue, but only if Ulster Scots speakers are included in any Act - a condition Sinn Fein has rejected.

Leading Democratic Unionist Edwin Poots said: "We will be happy to run D'Hondt (to select ministers) tomorrow and continue with negotiations in a fair and reasonable manner to get the solutions.

"It is up to Sinn Fein if they wish to do that, or if they want to break through the deadline that is a matter for them, but we are happy to nominate ministers tomorrow."

Ulster Unionist (UUP) leader Robin Swann said his party would not provide "cover" for the DUP if it signed up to an Irish Language Act.

He said there were many issues the UUP wanted to raise, including mechanisms for dealing with the legacy of the Troubles and pensions for conflict victims.

"Our party will not be taken for granted in these talks or the formation of any executive," he said.

Sinn Fein has hinted movement was possible on one precondition - its opposition to DUP leader Arlene Foster returning as Stormont First Minister while a public inquiry into a botched green energy scheme is ongoing - if the DUP gave ground on other matters.

Mrs Foster was forced from office in January when Sinn Fein's then deputy first minister, the late Martin McGuinness, quit in protest at the DUP's handling of the Renewable Heat Incentive (RHI) - a scheme that left the administration facing a £490 million overspend.

His move triggered a snap assembly election in March.

A number of attempts to restore powersharing between the five main parties following that poll foundered, with three UK Government deadlines for a deal having already been missed.

Earlier, Northern Ireland Secretary James Brokenshire said failure to strike a powersharing deal would have "profound and serious" implications.

The DUP was involved in a spat with the Irish government, which is helping lead the negotiations with its British counterparts, after it reiterated its commitment to an Irish Language Act.

Christopher Stalford of the DUP said: "By publicly declaring its support for Sinn Fein's position in negotiations, the Irish government has undermined its own credibility as being neutral."

Update 7.11pm: The DUP and Sinn Féin have been accused of a "no show" at the latest round table talks in Stormont.

Parties only have until tomorrow afternoon to elect ministers and save the power sharing institutions.

It is understood the two largest players instead held talks with each other over the issue of an Irish Language Act.

Ulster Unionist Leader Robin Swann says he is not in favour of it, claiming there are bigger issues to resolve.

"I will deal with legacy, the establishment of a historical investigations unit, how we look after our pensioners, our young people," he said.

Update 6.46pm: The UK and Irish governments must inject "leadership and energy" into last-ditch talks to restore powersharing in Northern Ireland, Sinn Féin has said.

Claiming the Democratic Unionists (DUP) were still standing in the way of a deal, Sinn Fein's John O'Dowd told the governments to ramp up their involvement in the stalled negotiations.

An impasse over republican demands for legislation to protect Irish language speakers is one of the main impasses. The DUP is willing to legislate, but only if Ulster Scots speakers are included in any Act - a condition Sinn Féin has rejected.

The parties have until 4pm on Thursday to nominate ministers to a new coalition executive or they face the prospect of some version of direct rule be imposed from Westminster or yet another snap Assembly election.

Emerging from the talks venue at Stormont Castle in Belfast, Mr O'Dowd questioned the merit of extending the deadline to facilitate further discussions.

"Timescale is not the issue," he said.

"It is a willingness by the participants in the talks to resolve the outstanding issues."

The Sinn Fein negotiator added: "There is clearly an onus on the governments to inject energy into these talks, to inject leadership into talks and ensure the outstanding issues are resolved in the time-scale we have left to us."

Earlier: Failure to strike a powersharing deal in Northern Ireland would have "profound and serious" implications, the British Government has warned.

Last-ditch negotiations led by the British and Irish governments on restoring a coalition ministerial executive at Stormont extended late into the night on Tuesday and are continuing on Wednesday.

The parties have until 4pm on Thursday to nominate ministers or face the prospect of some version of direct rule from Westminster or yet another assembly election.

Northern Ireland Secretary James Brokenshire told MPs: "Our focus is on seeing that an Executive is restored and I have been clear on not wanting to pre-empt what may happen should that not be the case.

"Obviously there would be profound and serious implications in that context."

He said he would work with all parties to see that the issues were considered carefully.

The two largest in Northern Ireland, the Democratic Unionists and Sinn Fein, remain at loggerheads over key issues like introducing an Irish Language Act to officially protect the minority tongue's use.

While it would be a major confidence-building measure for nationalists, DUP leader Arlene Foster has promised an act would not happen under her watch.

One alternative could be a law also covering the use of Ulster-Scots.

Irish is already used in settings like schools funded by the education system.

Sinn Fein has accused the DUP of refusing to budge on any of the substantive issues at the heart of the crisis.

The DUP urged the republican party to stop indulging in "high-wire acts" and get down to the job of delivering for the people.

Sinn Fein party chairman Declan Kearney hinted movement was possible on one precondition - its opposition to Mrs Foster returning as Stormont first minister while a public inquiry into a botched green energy scheme is ongoing - if the DUP gave ground on other matters.

DUP negotiator Edwin Poots suggested a "parallel process" could be initiated where an Executive is formed while talks on the outstanding issues continued.

Mr Kearney claimed the DUP was not prepared to move on republican demands for a stand-alone Irish Language Act, the introduction of same-sex marriage in Northern Ireland and a specific bill of rights for the region.

The peace process is littered with examples of apparently firm political deadlines being broken.

While Mr Brokenshire stressed the cut-off point was set in law, he did not definitively rule out another extension.

Mrs Foster was forced from office in January when Sinn Fein's then deputy first minister, the late Martin McGuinness, quit in protest at the DUP's handling of the RHI - a scheme that left the administration facing a £490 million overspend.

His move triggered a snap assembly election in March.

A number of attempts to restore powersharing between the five main parties following that poll floundered, with three UK Government deadlines for a deal having already been missed.