He said that after taking the file out of the safe at special branch headquarters in Hutton, Preston, he was contacted by an officer from MI5 who told him it needed to be sent to London.
Mr Robinson also disclosed that the then Director of Public Prosecutions had examined the allegations but decided they were “not in the public interest”.
He said: ”The police now say the file is lost. It seems like there was a complete cover up to me.”
In 1974 the Conservatives invited the Liberals to form a Coalition government in which Smith could have been appointed a minister. According to Mr Robinson a copy of the report from Lancashire Police was passed to Special Branch, which dealt with national security and intelligence. Mr Robinson, who had a previous interest in the case, said he read Sir Cyril’s file. He said: “I looked through Sir Cyril’s file which was kept in a safe in our office. “It was thick full of statements from young boys alleging abuse. It had been prepared for prosecution. “Written across the top of it were the words: ‘No further action, not in the public interest. DPP [Director of Public Prosecutions].’ “Shortly after taking it out I was called by an MI5 officer. They asked if I had the file on Mr Cyril Smith, and said: ‘Please have this sent down to London.” On Tuesday Simon Danczuk, the Labour MP for Smith’s former constituency in Rochdale, described him as a “29 stone bully” who “imposed himself” on his victims whom he “humiliated and terrified”. Mr Danczuk said some alleged victims had only now come forward in the wake of the Jimmy Savile scandal and it was time to find out “why was this allowed to happen”. Read more