Deputy First Minister Martin McGuinness blamed the “dark side” of policing for his leader’s detention during the election campaign and insisted Mr Adams could have been questioned without being arrested.
He said the questioning centred on books Mr Adams had written and what others said about him - those “maliciously and vehemently” hostile to the peace process.
He claimed: “People who could be described as former republicans (are) targeting the Sinn Fein peace strategy and targeting the leader of Sinn Fein, Gerry Adams.
“It has been disappointing to see the efforts of some of those people together in consort with the dark side within policing.”
He drew a contrast between “reformers” within the police service, whom he supported, and those from the “dark side” responsible for the arrest of his friend Mr Adams.
“For over 20 years we have worked very, very closely in developing the peace process, bringing about the political and security transformation that the public enjoy today and, in my opinion, in the course of supporting the peace process, he has been the single most influential figure in the process.
“I view his arrest as a deliberate attempt to influence the outcome of the elections that are due to take place in three weeks’ time, north and south on this island.
“That raises very serious questions around why that is the case and what is the agenda.”
Asked about claims that the arrest was politically motivated, Prime Minister David Cameron said: “There has been absolutely no political interference in this issue.”
He added: “We have an independent judicial system, both here in England and also we do have one in Northern Ireland.
“We have independent policing authorities, independent prosecuting authorities. Those are vital parts of the free country and the free society we enjoy today.”
PSNI Chief Constable Matt Baggott declined to be drawn into detailed comment on the arrest at a meeting of his oversight body, the Northern Ireland Policing Board, in Belfast.
He said the investigation would be “effective, objective and methodical”.
Asked about the McConville probe in the context of the legacy of the past, Mr Baggott said: “Effective investigation applies to any unsolved matter and it would be inappropriate for me to comment on any individual investigation other than to say they will be objective and methodical.”