Northern Ireland police were to decide on Friday whether to charge, release or apply for more time to question republican leader Gerry Adams over a notorious IRA murder in 1972.

The Sinn Fein president, who played a leading role in the peace process in the troubled British province, has been held for questioning since Wednesday night over the killing of mother-of-10 Jean McConville.

Adams has strongly denied any involvement in her murder, one of the most infamous in the three decades of conflict known as the Troubles, and his arrest has raised political tensions.

Police have until Friday evening – 48 hours from the time of his arrest – to question Adams before they must release him, charge him, or apply to a court for more time.

Deputy First Minister Martin McGuinness, a member of Sinn Fein, has condemned the allegations as “malicious” and designed to destabilise the peace process.

But British Prime Minister David Cameron insisted: “There has been absolutely no political interference in this issue.”

Any decision to charge Adams, who has led Sinn Fein since 1983 and is the public face of the movement to end British rule in Northern Ireland, could have huge ramifications.

The republicans and pro-British unionists agreed a peace deal in 1998 and Sinn Fein share power with the Democratic Unionist Party in a devolved government in Belfast.

McConville, a 37-year-old widow, was snatched from her home in west Belfast, becoming one of 17 so-called “disappeared” of the conflict.

The Irish Republican Army (IRA) paramilitary group admitted to her murder in 1999 and her body was found four years later, shot in the back of the head, on a beach.

Her children watched her dragged away but one of them, Michael, said he remained too scared of reprisals to give the names of the attackers to police.

But McConville’s eldest daughter, Helen McKendry, said she was ready to co-operate.

“I spent the first 20 years of my life being afraid of these people, of fearing to speak out, but now I am no longer afraid,” she told The Guardian newspaper.

Sinn Fein was once the political arm of the IRA, and although Adams insists he was never an official member, he played a key role in persuading it to give up its weapons.

The 65-year-old has long rejected allegations from other republicans that he ordered McConville’s murder, but he agreed to be interviewed by police.

“While I have never disassociated myself from the IRA and I never will, I am innocent of any part in the abduction, killing or burial of Mrs McConville,” he said on Wednesday.