Worries about costs could have played a role in delays in the investigation into missing ex-EastEnders actress Sian Blake and her children, an ex-murder detective with the Metropolitan Police has suggested.

The force has referred its handling of the case to the watchdog the Independent Police Complaints Commission (IPCC), amid questions over why it took so long to escalate the missing persons inquiry into the performer's disappearance

Murder squad detectives are still urgently looking for Ms Blake's boyfriend Arthur Simpson-Kent, who may have fled the UK after his family vanished.

Ms Blake vanished with her sons, Zachary, eight, and Amon, four, in east London on December 13.

The case was taken over by murder squad detectives on Monday, and three unidentified bodies were found the next day in the garden of the family home in Erith, Kent, that Ms Blake shared with her partner.

Former murder detective Colin Sutton said concerns over the costs of policing over the Christmas period may have been a factor in an apparent delay.

He told the Times: "There is greater pressure than ever not to waste money that may have influenced the decision making.

"It was the wrong decision and a bad decision and it's noticeable that as soon as everyone got back to work after Christmas on Monday morning that things really started happening."

The family of Ms Blake have said they "want answers" about why it took police nearly three weeks to find what are feared to be the bodies of her and her two sons.

One of the 43-year-old's aunts, who gave her name as Terry, has said relatives want "a full investigation".

On Wednesday the Met said: "An initial review has highlighted some potential issues regarding the handling and grading of the missing persons investigation."

Mr Simpson-Kent was interviewed by police at the family home three days after the actress went missing, before he also disappeared.

Asked about reports suggesting he has fled to Africa a Scotland Yard spokesman said: "Whether or not he is in the country is one line of inquiry."

Ms Blake had motor neurone disease - a fatal, rapidly progressing disease which affects the brain and spinal cord - and was reportedly looking "very frail" before she vanished.

She and her children were last seen in Waltham Forest, east London, and her silver-beige Renault Scenic was found in Calvert Avenue in Bethnal Green, east London, on January 3, but it is not known who parked it there.

Previously an unknown actress, Ms Blake's big break came when she was introduced as soul singer Frankie in EastEnders in June 1996 by series producer Jane Harris.

She was in the BBC soap for 56 episodes, reportedly quitting in 1997 because of hostility from viewers towards her manipulative character.

The performer, who later worked as a sign language tutor, also appeared in episodes of The Bill, Casualty, Doctors and Skins, and was the voice of Yugiri in 2015 video game Final Fantasy XIV: Heavensward.