Mr Baker, whose daughters Davina, 16, and Jasmine, 13, were murdered, said words were not enough to express his feelings.

Kumari-Baker, 41, was found guilty of murder on Monday following a trial at Cambridge Crown Court.

On Tuesday Judge Mr Justice Bean imposed two mandatory life sentences and said Kumari-Baker should serve 33 years before being considered for parole.

During the two-week trial, jurors heard that Kumari-Baker attacked the girls in the early hours of June 13, 2007 as they slept at her home in Stretham, Cambridgeshire.

She first walked into Davina's bedroom and stabbed her eldest daughter 37 times, then moved into Jasmine's bedroom and stabbed her 29 times.

Evidence showed that Davina - whose body was found kneeling on the floor - had struggled. Jasmine was found dead in bed.

Kumari-Baker attacked the girls with two kitchen knives she bought at an Asda supermarket two days earlier, prosecutors said.

Jurors were told that Kumari-Baker was unhappy about a new relationship her ex-husband had entered into.

She was also upset by the break-up of her new relationship with boyfriend Jeff Powell.

Prosecutors suggested that she murdered the children in an attempt to "wreak havoc" on her ex-husband.

Psychiatrists called by the prosecution said Kumari-Baker was suffering from mild depression but did not have a mental disorder or mental illness.

Kumari-Baker mounted a "diminished responsibility" defence - with lawyers arguing that she had an abnormality of mind which would make her guilty of manslaughter but not murder.

The jury of seven women and five men took 35 minutes to conclude that she was guilty of murder.

Kumari-Baker has already spent two years and 92 days in custody and therefore has at least 30 years and 273 days left of her sentence.

The judge said the Parole Board would not consider her for release until 2040, when she will be 72.

Prosecutor John Farmer read extracts from Mr Baker's victim impact statement today as the judge prepared to pass sentence.

"My words may not be sufficient," said Mr Baker in the statement.

"Having them taken away from me in such a brutal way and by the woman who was their mother... has had an incalculable effect."

Mr Baker's statement said he suffered from feelings of guilty and helplessness.

"She tore them from us all and life can't be the same for those who remain."

He added: "Each birthday since has been almost unbearable as I think of what they might have been doing."

Mr Baker said he had been incapable of working since and had attended counselling, but found it of little help.

"Nothing will ever bring my girls back or undo this monstrous act," he said.

"I will never see them again in this life, though they live in my heart."

Mr Justice Bean said Kumari-Baker had been found guilty of two brutal murders on the basis of "clear and compelling evidence".

"Most people will find it inexplicable that a mother could kill her own children and you have given no explanation for it," he said.

"You were certainly upset at the breakdown of your relationship with Jeff Powell.

"On the basis of the evidence of (psychiatrists), I think (a) mild depression was probably combined with a wish to retaliate against David Baker and destroy the happiness in his life.

"But to some extent your motive remains a mystery."

He added: "Despite the diligent and professional efforts of your legal team, the evidence in support of your defence of diminished responsibility was flimsy and unsubstantial.

"You knew quite well what you were doing and you were not mentally ill.

"The crimes were, as the prosecution rightly put it, murder, full stop.

"Davina and Jasmine were cruelly cut down in the prime of life. Their death has been a shattering loss to their father and friends."