A west Auckland mother who admitted seriously abusing two of her children has failed in a bid to have her prison term reduced.

The woman, whose name is suppressed to prevent her children being identified, was jailed for seven and a half years, with a minimum term of five years, in December last year.

She admitted 25 charges of abusing her nine-year-old daughter and seven-year-old son.

When sentencing her Auckland District Court judge Brooke Gibson said she had subjected her daughter to "sustained cruelty, amounting to torture" over a number of months in 2010, and that the injuries inflicted were "the most serious possible harm, short of death".

Her lawyer, Lorraine Smith, argued that the overall effect sentence was excessive, and the minimum non-parole period should be reduced to take into account her previous good character, her daughter's behavioural issues and the fact that she too was an abuse victim.

But the Court of Appeal noted that they were arguments that were raised at sentencing and the original sentence was fully justified and the judge was entitled to impose a five-year minimum term.

At the woman's sentencing, the court heard that the girl had been kicked with steel-capped boots, had a hammer thrown at her foot, fracturing her toes, and had a toenail ripped out and hot water and salt poured over it.