The family of a brother and sister murdered in a deliberate fire have spoken of their devastation and anger as they made a plea for information.

Eight-year-old Bridget Sharkey and her brother Thomas, 21, died after the fire at their home in Helensburgh, Argyll and Bute, in the early hours of Sunday.

Their parents, Thomas Sharkey, 55, and his wife Angela, 46, suffered serious burns and are still in a critical condition in hospital.

Mr Sharkey, who is in Glasgow Royal Infirmary, was told of his children's deaths on Tuesday. His wife, who has been moved to the same hospital, does not yet know.

Today, Valerie McFadyen, Mr Sharkey's sister, read a statement on behalf of the family.

Speaking at the town's police station, she said: "The entire family have been left shattered, devastated and now angry by the deaths of our darling Bridget and Thomas.

"Golf was Thomas's life and all his family and friends aspired to be as good as he was. His smile lit up every room and he always found the best in everyone he met. We always thought he would be famous for his golf and not for the tragic way he died."

Mrs Sharkey's sister Margaret McKechnie held back tears as she then spoke.

She said: "Bridget was a bubbly, cheeky and extremely popular girl who loved dancing and going to Brownies. In her short life she touched so many people's hearts and we will all miss her so much and Angela has lost her best friend."

She added: "The whole family had some precious final days together when they travelled to Florida for a holiday. Thomas and Angela had never seen their wonderful children so happy as the day they both swam with dolphins. Thomas now has the difficult job of introducing Bridget to her two grans who are now looking after them in heaven.

"We would like to thank everyone for the messages of condolence and support. Thank you all for your help and please keep doing everything you can to help the police to find those responsible."

Emergency services were called to the fire at the flat in Scott Court at around 5.10am on Sunday. The fire broke out in the living room and quickly spread. Police said the building had just one door and the family was trapped.

Mr Sharkey was seen hanging out of the window and shouting for help. His son was found dead at the scene. The rest of the family were taken by ambulance to Royal Alexandra Hospital in Paisley, Renfrewshire, where Bridget died a short time later.

Strathclyde Police said more than 50 officers are working on the murder investigation. Crimestoppers is offering a s10,000 reward for information which leads to the arrest and conviction of whoever committed the crime.

Detective Chief Inspector Anne McKercher, of Strathclyde Police, said: "We are continuing to follow a number of lines of inquiry from the calls we have received so far, as well as information gleaned from the local community. We are greatly encouraged by the response and would like to thank local people for their help and support.

"Once again we would urge anyone with any information to contact the incident room on 01389 822 059 or call Crimestoppers, where you can give your information anonymously, on 0800 555 111."