Mairead Philpott was jailed for killing her six children in a house fire.

A mum who killed her six children in a house fire has been freed after serving just half of her 17-year sentence, causing outrage across the UK.

Mairead Philpott, 39, and her husband Mick Philpott killed their children during an arson attack on their own home in Derbyshire in 2012.

But after serving just eight-and-a-half years for manslaughter, Mairead has been freed.

Her release has sparked fury, with crime-prevention campaigners saying: "Justice has not been done."

"It makes an absolute mockery of the UK's criminal justice system. Justice has not been done," said David Spencer of the Centre for Crime Prevention.

"Child killers like Mairead Philpott should not be free to roam the streets.

"She has served barely more than a year for each of the six innocent lives she callously took away.

"She is back on the streets while the taxpayer coughs up for her to get a new identity, protection, ­counselling and a place to live.

"The Home Secretary has promised a review of sentencing. This needs to be delivered urgently to ensure killers like Philpott serve the long sentences their horrific crimes deserve."

Mairead's mother Vera, who has cut ties with her daughter, told The Sun she was appalled her daughter was released early, saying: "I don't want her near my door.

"The sentence is not nearly long enough and we disown her after what she's done."

Mick Philpott, Mairead's husband is still in jail after he was found guilty of manslaughter and given a life sentence with minimum parole of 15 years' imprisonment.

Mick had first come to prominence in the British media as a result of his large family (having fathered 17 children by various women) and his reliance on state benefits.

On May 11, 2012, the Philpott home was seriously damaged by fire around 4am.

Five of his children, who were asleep upstairs, all died at the scene, while their half-brother died two days later.

The Philpotts held an emotional news conference, in which they purported to describe the events concerning the fire and plead for help.

Later, police stated that petrol had been found inside the letterbox to the Philpott residence, thus sparking a murder investigation.