First Minister Nicola Sturgeon has told how her "heart breaks" for the family of murdered schoolgirl Paige Doherty after her killer had his sentence cut by four years.

John Leathem was given a mandatory life sentence and ordered to spend at least 27 years behind bars for the frenzied knife attack on the 15-year-old.

Leathem admitted killing the teenager after she came into his deli-shop in Clydebank, West Dunbartonshire, in March 2016.

Last week, less than a year after Paige's death, judges at the Appeal Court in Edinburgh quashed the original punishment and imposed a 23-year minimum sentence.

The decision prompted Scottish Conservative leader Ruth Davidson to call for whole-life sentences to be introduced north of the border.

She challenged Ms Sturgeon on the issue at First Minister's Questions at Holyrood, saying if the Scottish Government did not act her party would bring forward a member's bill to try to make the change.

Ms Davidson said: "As it stands, our judges do not have the tool of a whole-life tariff at their disposal and we say that we should.

"We can sit in this Parliament and we can wring our hands and we can express outrage every time something like this happens, or we can do something about it.

"I want to do something about it."

She pledged: "If the Scottish Government won't act, then I can say the Scottish Conservatives will do so by pushing ahead with a member's bill making the case for the introduction of whole-life sentencing in Scotland.

"We need to stand up for families who see sentences for murder cut less than a year after they have been handed down and we should change the law so that families like Paige Doherty's feel that the law is tipping back in their favour and that the worst criminals are kept off our streets forever."

Ms Sturgeon said her government would "reflect further" on the issue "about what further changes we might think appropriate".

The First Minister said: "My heart breaks for the family of Paige Doherty.

"I met Paige's mother last year and there literally are no words to express the pain and grief that she and the rest of her family have gone through."

She said she had "no difficulty" understanding comments made by the Justice for Paige campaign group, who branded the reduction in Leathem's sentence as "heartbreaking", arguing that it "serves no justice to Paige and her family"

Ms Sturgeon said: "If I had been a relative of Paige Doherty, I would have felt exactly the same."

In what she said were "absolutely frank" comments, the SNP leader added: "As well as being First Minister, I'm also a human being and there are many occasions when I look at decisions of courts and wish that different decisions had been reached. It may well be this is one such case."

She stressed: "This was the decision of an independent judge in a court of law. We have an independent judiciary in this country."

Ms Davidson had said it was "entirely unacceptable that less than a year after watching her daughter's killer get locked up, families should then go through the ordeal of seeing that murderer's sentence reduced".

The Conservative pressed Ms Sturgeon on the need for whole-life sentences, which are available to judges south of the border.

She told the First Minister: "We on these benches say there must be change, because a system which cuts a child murderer's sentence because he is deemed not as bad as others is rightly seen by most members of the public as a disgrace.

"The problem here isn't just the Paige Doherty case, there are too many families who have seen their loved ones killed who do not feel they are getting the justice they deserve, who feel that the dice is loaded against them and in favour of the criminals.

"We have long campaigned for whole-life sentences to be introduced in Scotland so that judges could, if they wish, sentence the very worst criminals to spend the rest of their lives in jail."

Ms Sturgeon said the Government would consider if change was needed but stressed that the independence of the judiciary meant there would always be some cases where sentencing decisions come in for criticism.

Regarding the decision to cut Leathem's jail term, she said: ""This was the decision of an independent judge in a court of law. We have an independent judiciary in this country."

The First Minister added: "No matter what framework and context Parliament sets on any of these issues, we will still have instances where decisions by courts are decisions that many people feel are the wrong decisions. That's in the very nature of an independent judiciary.

"But I am very clear that where there is evidence the law has to be changed or action has to be taken, then that is something this Government and this Parliament should reflect on very seriously.

"That includes the experience of the particular tragic case we are talking about today."

She said the SNP in government had made changes to the legal system which had improved the justice system over the last decade.

However, she also pledged the Government would "continue to look with an open mind at proposals that are brought forward for further reform".

Ms Sturgeon said: "If the system that Ruth Davidson is advocating for had been in place - and this is an important point - in this and in any other case, there is no guarantee that that is the sentence a particular judge would have opted for.

"I am simply making the point that even if we had - and I'm not saying it is the wrong thing to be considering - the point I am seeking to make is this, we will always have cases no matter what the sentencing options that judges have, where a judge makes a decision that some people do not think is correct."

A Scottish Government spokesman said: "The murder of Paige Doherty was shocking and all our sympathies continue to go to Paige's family and friends.

"As the First Minister said, sentencing in any given case is clearly a matter for the courts, however the law in Scotland is clear that a life sentence will be imposed on anyone convicted of murder and, as part of that, the court may impose a punishment period extending beyond the remainder of a prisoner's life.

"An offender convicted of murder can receive a sentence which means they are never able to be considered for parole, which is in effect a whole life sentence.

"As the First Minister also made clear, the Scottish Government will reflect further whether there is a need to consider possible changes in this area."