Deputy First Minister Martin McGuinness, the senior Sinn Fein figure in the power-sharing government in Belfast, repeated his claim that the arrest of the party's leader on Wednesday was politically motivated.
And he warned that a bid by the Police Service of Northern Ireland (PSNI) to extend their questioning of Adams beyond the provisional 48 hours was causing growing anger.
"Yesterday I said that the timing of the arrest of Gerry Adams was politically motivated. And today's decision by the PSNI to seek an extension to his detention absolutely confirms that view," McGuinness told reporters.
Adams, who played a leading role in the peace process in the troubled British province, strongly denies involvement in the abduction and murder of Jean McConville.
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The widowed mother of 10 was snatched from her Belfast home in one of the most infamous cases of the three decades of sectarian conflict known as The Troubles.
She became one of 17 so-called "disappeared" until the Irish Republican Army (IRA) paramilitary group claimed her murder in 1999. Her body was found four years later.
But he warned that if Adams were charged, Sinn Fein might "review" its support for policing, which is fundamental to the success of the Northern Ireland government, where Catholic Irish nationalists share power with pro-British Protestants.
McGuinness accused the "dark side" of policing for conspiring with republican enemies of the peace process.
Northern Ireland Justice Minister David Ford, a member of the cross-community Alliance party, said there was "no evidence" of political policing.
"There is no reason why the police carrying out their proper duties in the proper way should cause any political instability," he said.