The First Minister, David Trimble, says his Ulster Unionist party will quit by next Tuesday, unless another political party Sinn Fein is expelled.
Has there been spying?
At the moment they are among several parties who are sharing power.
But Sinn Fein - which used to be linked to terrorist group the IRA - has been accused of spying.
Three men have been accused of possessing information which could be useful to terrorists.
David Trimble says it's "no longer sustainable" for his party to share power with them, and wants UK Prime Minister Tony Blair to sort it out.
Other politicians have already quit, and it's led to the biggest crisis in Northern Ireland for several years.
If the power-sharing group does collapse, Northern Ireland might have to be ruled by the UK Government, which they want to avoid.
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