LONDON/BELFAST (Reuters) - The British government’s Northern Ireland minister warned on Tuesday that an early election in the province was highly likely following the resignation of deputy leader, Martin McGuinness, which effectively collapsed its devolved government.

Britain's Secretary of State for Northern Ireland James Brokenshire arrives at 10 Downing Street for a cabinet meeting, in London, November 15, 2016. REUTERS/Peter Nicholls

McGuinness resigned on Monday in protest at First Minister Arlene Foster’s handling of a controversial green-energy scheme, risking political paralysis in the region as Britain plans its exit from the European Union.

“I am very clear that in the event of the offices not being filled, I have an obligation to follow the legislation. As things stand therefore, an early assembly election looks highly likely,” Secretary of State for Northern Ireland James Brokenshire told parliament.

“The situation we face in Northern Ireland today is grave and the government treats it with the utmost seriousness,” Brokenshire said.

McGuinness, who quit after Foster repeatedly refused to step aside for the duration of an inquiry into the botched “cash for ash” scheme, has said his Irish nationalist Sinn Fein party will not nominate anyone to fill the office that is jointly held with Foster’s pro-British Democratic Unionist Party (DUP).

Foster said on Tuesday she is open to talks with Sinn Fein but their continued refusal to replace McGuinness will cause the power-sharing government to end in six days’ time when Brokenshire must propose a date for the election.

“If necessary we will take our case to the electorate and use it as a platform for further discussions,” Foster said in a statement.

Brokenshire said there was a widely held view an election will change nothing and instead would threaten the continuity of the devolved institutions.

“This political stability has been hard-gained, and it should not be lightly thrown away,” he added.

Sinn Fein President Gerry Adams said he did not think elections could be avoided and Mike Nesbitt, the leader of the Ulster Unionist Party, the province’s second-largest pro-British party, said they were inevitable.

Adams also echoed comments by McGuinness on Monday that raised the prospect of a lengthy renegotiation between the two divided governing partners on the terms of power-sharing, part of the 1998 Good Friday peace agreement.

That deal ended three decades of violence between mainly Catholic Irish nationalists seeking a united Ireland and Protestant pro-British unionists who wanted the North to remain part of the United Kingdom.

While the violence, which killed over 3,600, has subsided, the two sides of the sectarian divide have consistently strained at the confines of their power-sharing arrangement.