LONDON (AP) — The future of the Catholic-Protestant power-sharing government in Northern Ireland is hanging by a slender thread with First Minister Peter Robinson's decision Thursday to step down, along with all but one of his ministers, because of a series of disputes.

Democratic Unionist leader Robinson left one party figure, Arlene Foster, in place as temporary first minister and finance minister, but the coalition government has been seriously weakened by developments and may ultimately be suspended, leading to a restoration of direct British rule from Westminster.

The crisis stems in large part from a police finding that that Irish Republic Army dissidents were involved in last month's killing of former IRA member Kevin McGuigan, a development that Robinson said raised serious doubts about the future of the coalition government that is a prime achievement of the 1998 peace agreement.

Robinson said "business as usual" is impossible because of "the assessment of the chief constable of the involvement of the IRA in murder, the continued existence of IRA structures, and the arrests that followed has pushed devolution to the brink."

He said he was leaving Foster in place as a gatekeeper to prevent other parties from taking advantage of the situation in what may be the final days of the power-sharing government.

Robinson said crisis talks with the government will continue. Downing Street officials said Prime Minister David Cameron is "gravely concerned" by the developments and that he will seek a solution.

The unlikely coalition of former enemies, formed in 2007 after earlier governments were suspended, has lasted for eight years, longer than many had expected.

But it hasn't functioned fully for the past year, with Catholic-based parties blocking budget plans because too many British-ordered welfare cuts were involved.

There had been four earlier suspensions of the Northern Ireland government since the 1998 peace agreement was reached after years of delicate negotiations that followed the IRA's declaration of a cease-fire.

If direct rule from Britain is imposed again, it would mark the first time since 2007 that decisions would be made in London, not Northern Ireland.

Sinn Fein President Gerry Adams called for more talks so that the government could continue to operate.

He spoke before Robinson stepped down, but after several parties including Sinn Fein had voted against Robinson's request that the government be suspended to give delicate negotiations a chance to bear fruit.

Several prominent figures have been arrested as part of the murder investigation in recent days, including Sinn Fein regional chairman Bobby Storey. They remain in custody but have not been charged.

The killing was a suspected revenge attack for the killing of a former IRA commander several months earlier.

Critics say the killings show the IRA remains an active and violent paramilitary force despite the peace agreement.