This article is more than 4 years old

This article is more than 4 years old

Leon Brittan’s brother has demanded an apology from Tom Watson, the Labour deputy leader, for making “unfounded” sex crime allegations about the former home secretary.

Sir Samuel Brittan, 83, called on Watson to say sorry directly to his sister-in-law, Lady Brittan, for wrongly accusing her late husband of rape and child abuse. He claimed Watson had damaged Lord Brittan’s reputation with “unforgiveable” slurs.

Following Brittan’s death, Watson wrote an article describing how the peer stood “accused of multiple child rape” and repeated accusations he said came from victims that he was “as close to evil as any human being could get”.

During his lifetime, Brittan consistently denied allegations of sexual abuse.

Watson has been a central figure in making claims of the existence of an establishment paedophile scandal, and played a key role in having a rape case against Brittan reopened after it was closed because of a lack of evidence.

The Labour MP would argue that he was campaigning more broadly on an issue of genuine national concern and merely wrote to the country’s prosecutors to ask them to look again at the case.

Other allegations Watson had made on behalf of victims of child abuse have led to prosecutions, and he believes it is his responsibility to pass credible allegations to the police.

The late peer was questioned under caution while terminally ill with cancer last summer, but police concluded that there was nothing in the allegation to merit further action.

However, Brittan was not informed by the police of their decision before his death, and his widow Diana was only told that was the case in the past week.

Facebook Twitter Pinterest Labour deputy leader Tom Watson played a key role in having a historical rape case against Leon Brittan reopened. Photograph: Ben Pruchnie/Getty Images

The force’s oversight was criticised by the mayor of London, Boris Johnson. He told the Daily Telegraph: “I welcome the fact that the Met has now apologised to Lady Brittan. It is clear that the delay in informing her that there was no case to answer is completely unacceptable and I have raised the matter with the commissioner.”

Johnson, a supporter of Bernard Hogan-Howe, the Metropolitan police commissioner, will be jointly responsible with Theresa May, the home secretary, in deciding whether to extend Hogan-Howe’s contract when it expires in September.

The Met’s deputy assistant commissioner, Steve Rodhouse, conceded that the Met should have provided clarity over the case earlier and apologised for the distress this caused.

Samuel Brittan, the retired former Financial Times executive and columnist, trained his fire on Watson: “He should apologise to my sister-in law for making unfounded accusations against my brother. And he should apologise in public as well.”

He also condemned police for their “outrageous treatment” of his brother, adding: “I was brought up with people saying the English police were wonderful. I’m not sure I could repeat that now.”

Former chancellor Norman Lamont, writing in the Daily Telegraph, attacked the police saying: “After Lord Brittan’s death came the police raid on his two houses, while his widow was still sorting out his belongings, some of which were carted away. As with Cliff Richard … BBC journalists told people that they had been tipped off by the police.

“Before Lord Brittan died, the police, referring to a rape accusation, suggested he should take part in identity parade. seems beyond satire. How could a well-known public person, already named and identified by his accuser, usefully take part in such a charade?”

He said: “I visited Leon Brittan, several times in his last days and saw the suffering of a man under the shadow of the vilest accusations. This was an extremely painful time for his wife.”

Scotland Yard investigated the allegations from a woman known as “Jane”, which first surfaced in 2012, but after consulting the Crown Prosecution Service decided not to take the investigation any further and Brittan was informed he was in the clear.

But in May 2014, Watson wrote to the Met and Alison Saunders, the director of public prosecutions, to complain that the investigation had been dropped without interviewing Brittan.

On Thursday night, Keith Vaz, the chairman of the powerful Commons home affairs select committee, wrote to the Met demanding answers over the case, and asking how the police seemed so incapable of admitting error.

Brittan – then terminally ill – was interviewed under caution and had the allegation hanging over his head when he died in January, aged 75.