Metropolitan Police has defended how it managed a sexual assault investigation against Leon Brittan after it was forced to apologise to his widow for not informing him a case would not be brought forward while he was still alive.
Scotland Yard said it has asked for a separate police force to review the Met investigation against the former home secretary to ensure it was "thorough, properly conducted and to identify good practice".
The former Tory minister died in January aged 75 unaware that police had dropped a case against him over allegations he raped a 19-year-old in a flat in London in 1967, which had been reopened in 2014.
Police first received a complaint in 2013, which Brittan was neither informed about nor interviewed over. Detectives from the MPS submitted a file to the Crown Prosecution Service (CPS) for '"early investigative advice" to provide guidance and advice in serious, sensitive or complex cases.
The CPS made the decision that no further action should be taken and the complainant was informed in person in September 2013, but not Brittan.
Brittan was then questioned but not arrested in June 2014, just a few months before he died of cancer, after Labour's deputy leader Tom Watson wrote to Alison Saunders, the director of public prosecutions, asking her to re-examine the case after speaking to the woman, referred to only as "Jane".
In April, officers met with the complainant in line with the Victim's Code, and informed her that there would not have been a prosecution had Brittan been alive. She was told the CPS would not review the file and that the matter was now closed.
During a detailed explanation of the process during the investigation, the Met said it could not have informed the former home secretary that it had decided not to bring charges because the force was asking the CPS to review its decision. The Met added this was because if it had immediately dropped the case the force would have been susceptible to "media criticism and public cynicism".
A spokesperson said: "It was felt that these were highly unusual circumstances where the previous independence of the police to tackle sexual offending by VIPs had been publicly called into question.
"A decision to take no further action in respect of this allegation would undoubtedly have resulted in media criticism and public cynicism, and there was clearly a very strong public interest in ensuring that the correct decision had been made.
"Lord Brittan could not therefore, at that point, have been informed that no action was to be taken in respect of this allegation. Although the MPS had concluded that there was not a strong case against Lord Brittan, the purpose of requesting a CPS view was to assess whether, in its view, it did reach the evidential standard.
"It would have been open for the CPS to conclude that it did not meet the threshold for charging and no further action should be taken, or that further enquiries were needed, or that there was in fact sufficient evidence for a charge. It was therefore conceivable that a reviewing CPS lawyer could have concluded that Lord Brittan could have been charged."
The spokesperson added: "The MPS accepts that Lord Brittan's solicitors should have been informed at the same time as the complainant was informed. This would have permitted them to clarify the position with Lady Brittan, for which the MPS apologised in a letter to her solicitors on 6 October 2015.
"There had been no previous contact between the MPS and Lady Brittan during the investigation as it is not normal procedure to inform anyone other than the person accused of the offence.
"Relatives of people who die whilst under investigation would not normally be contacted after their death and would not be told what the outcome of the investigation would have been, or indeed whether it would have led to a charge or not.
"But the MPS recognises – as it did throughout the dialogue with the CPS – that the public interest in the case required a different approach."