Baby Dylan with his mother and Metcalfe

Ian Metcalfe, 35, was jailed last year after being found guilty of culpable homicide by a jury at the High Court in Edinburgh.

However, the Crown lodged an appeal against the sentence on the grounds that it was "unduly lenient".

On Thursday, three appeal court judges quashed the jail term and replaced it with a sentence of 10 years.

Metcalfe, from Locharbriggs, Dumfries, was originally charged with the murder of Kyle Metcalfe, who was 11 weeks old when he died, and Dylan Lockerbie, who was aged five months.

He was convicted of the lesser charge of culpable homicide after a trial.

Cot death

The court heard that Metcalfe suffocated the two boys by putting his hand over their mouths.

Kyle's death in 1988 was initially blamed on cot death.

However, police began an investigation when Dylan, who was born to a different mother, died in 1996.

Metcalfe was also convicted of suffocating and endangering the life of a third child, who cannot be named for legal reasons.

Seven years was not just a lenient sentence but an unduly lenient one Advocate Depute Calum MacNeill

On Thursday, Advocate Depute Calum MacNeill told the appeal judges that Metcalfe was "in the ultimate position of trust".

"His duty was to nurture and protect these defenceless infants," he said.

"He committed assaults resulting not in the death of one child but in the death of two children.

"Seven years was not just a lenient sentence but an unduly lenient one."

Mr MacNeill said Metcalfe had been found guilty of repeated minor assaults on children over the course of eight years.

The youngsters sustained bruising, broken ribs and internal bleeding.

No remorse

Mr MacNeill argued that Metcalfe was a danger to young children.

He said that the civil engineer, who still denies the assaults, had not pleaded guilty or shown any remorse.

Donald Findlay QC, representing Metcalfe, said the jury had ruled that his client did not deliberately kill his children, but had lost control of himself.

He said he was no longer a risk to babies because he would never be allowed to keep any children in the future.

At risk register

Mr Findlay also claimed that the Metcalfes had asked for help from Dumfries and Galloway Council's social work department when they struggled to cope with Dylan Lockerbie, but received none.

The local authority admitted failings in their dealings with the family and said they were wrong not to place the infant on the "at risk" register months before he died.

It described Metcalfe as a repeat offender who covered his tracks well and was only brought to justice thanks to advances in forensic science.