DUBLIN — Northern Ireland’s power-sharing government was plunged into crisis Monday as its senior Catholic leader quit in a showdown with his Protestant colleague that could trigger a snap election and shatter the bedrock of the region’s peace deal.

Deputy First Minister Martin McGuinness, the former Irish Republican Army commander who has helped to lead the unity government for nearly a decade, said his resignation was the only effective way to challenge his power-sharing partner, First Minister Arlene Foster.

She will be forced from office, at least temporarily, if an election is called.

In his resignation letter, McGuinness accused Foster of ignoring ‘‘a public mood that is rightly outraged at the squandering of public money and allegations of misconduct and corruption.’’

The government, formed under terms of Northern Ireland’s 1998 Good Friday peace accord, requires support from McGuinness’s Irish nationalist Sinn Fein party and Foster’s Democratic Unionists, which represents the British Protestant majority.

Their unlikely partnership has been credited with governing the long-disputed corner of the United Kingdom in relative harmony following four decades of bloodshed that claimed 3,700 lives.

But tensions between Sinn Fein and the DUP have come close to a breaking point several times. And from the shadows, splinter groups opposed to the IRA’s 2005 disarmament and renunciation of violence still seek to sow division and disorder.

Associated Press