There is "overwhelming" evidence Sir Cyril Smith sexually abused young boys and authorities missed the chance to prosecute the late Liberal Democrat MP three times.
Police acknowledged for the first time on Tuesday evening that Smith sexually and physically abused young boys in the 1960s.
Smith, who was elected to Parliament in 1972, was dogged by rumours of abuse throughout his career but charges were never brought.
Both Greater Manchester Police (GMP) and the Crown Prosecution Service (CPS) said if Smith had been accused today he would be charged and prosecuted.
A GMP spokesman said: "The Force is now publicly acknowledging that young boys were victims of physical and sexual abuse committed by Smith.
"Three separate files regarding Sir Cyril Smith's actions were passed to first the director of public prosecutions (DPP) and the Crown Prosecution Service although on each occasion no prosecution was pursued."
According to Greater Manchester Police, which has now assumed full responsibility for the case, prosecutors were given evidence about Smith three times - in 1970, February 1998 and March 1999 - and each time missed their chance.
The "larger than life" former MP for Rochdale, who died in 2010 aged 82, is thought to have routinely molested young boys.
The GMP's assistant chief constable Steve Heywood said in a statement released on Tuesday evening it time to acknowledge the suffering of Smith's victims.
"It is absolutely important for those victims who were abused by Smith that we publicly acknowledge the suffering they endured.
"Although, Smith cannot be charged or convicted posthumously, from the overwhelming evidence we have it is right and proper we should publicly recognise that young boys were sexually and physically abused and we will offer them as much support as they need should they wish to speak to us."
"Having now reviewed those decisions, we believe that if the same evidence was presented to the CPS today there would have been a very realistic prospect that Smith would have been charged with a number of indecent assaults, and that the case would have been brought to trial," he said.
Sir Cyril was widely praised by his peers when he died, with Lib Dem leader Nick Clegg calling him "a larger-than-life character and one of the most recognisable and likeable politicians of his day."
But former residents at a boys hostel in Rochdale alleged in an investigation by PoliticsHome that they had been subjected to "medicals" where they had their buttocks and testicles stroked, and their bare bottoms slapped by Smith in the 1960s.
PoliticsHome interviewed Barry Fitton and Eddie Shorrock, who were 15 and 17 at the time, both who allege were given intrusive "medicals" by Smith, a local councillor at the time and one of the founders of the hostel, where most boys were from disadvantaged backgrounds, abuse victims or on probation. Fitton said he made an allegation against Smith in 1979.
Current Rochdale MP Simon Danczuk has demanded an inquiry into the claims amid accusations of a "cover-up."
"Smith abused his power beyond belief. How many more people were victims? There are a lot of allegations coming forward now."
Heywood said: "Lastly, I want to add my sympathies to anyone who was a victim of sexual or physical abuse by Sir Cyril Smith. Having reviewed the full history of this case, I am satisfied that numerous attempts were made to expose his activities but for various reasons this did not happen.
"That will be of little comfort to the people who were brave enough to recall their traumatic experiences, but will never see justice done in court. However, I hope that by publicly acknowledging what happened 50 years ago it will give those people some sense of justice."
A Liberal Democrat spokesman said: "These allegations are abhorrent and should be taken very seriously.
"Clearly the party does not endorse any person proved to have been in incidents such as these.
"All allegations should have been investigated thoroughly with the authorities taking whatever action necessary. Any new allegations should be made to the police.
"The Liberal Democrats are not aware of any allegations being made to the party, and have never been involved in any investigations.
"The alleged incidents and the reported police investigations took place outside of the time Cyril Smith was a Liberal MP."
11 March 1970 - file was submitted to the then Director of Public Prosecutions following a thorough investigation in 1969 by Lancashire Police, which detailed allegations from eight young people at Cambridge House Hostel about indecent assaults committed by Sir Cyril Smith.
19 March 1970 - the DPP recommends no further action be taken.
February 1998 - While conducting a review of care homes in their area another police force referred a complaint to GMP made by one of the original complainants of the 1969 inquiry who was unhappy with the result. This complaint was recorded and investigated by GMP as part of a wider investigation into care homes in Greater Manchester, and a file of evidence was submitted to the CPS for a review.
June 1998 - GMP was advised no further action would be taken.
March 1999 -a second file was sent to the CPS by GMP following two further complaints that were made about Smith's actions at Cambridge House Hostel between 1962-1965. Again, no further action was recommended by the CPS.
*source = Greater Manchester Police