A whistleblower raised concerns about a cover-up in Kingston Council’s social services one hour before she walked out of the authority for good, it has been revealed.

Kingston Council said it did not learn of allegations of a cover up in the Charito Cruz case until a BBC report last month, when Olivia Butler, former head of social services, told the broadcaster two social work managers changed computer records following the 37-year-old’s murder in September 2011.

Council leader Derek Osbourne criticised Ms Butler in a public statement, saying she should not have waited 16 months to make the claims.

But the authority has confirmed Ms Butler sent an email to ex-director of children’s services Duncan Clark and an HR manager on the afternoon of November 24, 2011 – her last day at the authority – advising disciplinary action against the staff members.

The council declined to release the full email, citing personal information subject to the domestic homicide review into Ms Cruz’s death.

A council spokesman said following the BBC story, the council reviewed its records and found Ms Butler had spoken and written to both managers, before emailing Mr Clark.

He said: “After Olivia Butler made her allegations to the BBC we examined our records.

“Our examination of the record reveals that on the November 24, Olivia Butler wrote an email to Duncan Clark and the author of the internal management review summarising the main points she had made in her letters to the two managers.

“It is clear from this that the views that Olivia Butler expressed at the time were taken into account in the writing of the internal management review.

“The email of November 24 says ‘Duncan, my professional advice to you is that formal management action should be seriously explored in relation to some of their actions and decisions’.

"This is the first reference the council has seen to Olivia Butler mentioning the possibility of disciplinary action. Her own letters to the two team managers do not mention disciplinary action.”