David Smith, an officer with the Ministry of Defence at RAF Menwith Hill, near Harrogate, had been living with Susan Phillipson for five years before he died in September, 2007.

The court heard the couple's relationship had "soured" and they planned to split up.

On the night of his death, Mr Smith revealed to Phillipson he was planning to emigrate to Canada with another woman - and they argued, with fatal consequences.

Phillipson (41), of Skipton Road, Barnoldswick, admitted manslaughter at Preston Crown Court in November, 2007 and was sentenced to three years and four months behind bars.

But yesterday, her legal team urged Lord Justice Latham, Mr Justice Grigson and Mr Justice MacDuff to reduce her sentence - as she had not intended to kill or cause serious harm to Mr Smith.

Mr Justice MacDuff said Mr Smith was preparing dinner when he began to row with Phillipson. He held the knife to his chest - but it was Phillipson who "tapped" it in.

She later told police she had been in a "distressed state" and had pushed the knife with the palm of her hand "on the spur of the moment".

The judge said it was a "sad case for all concerned", but Phillipson's sentence had been "merciful".

Dismissing the appeal, he concluded: "A sentence of this length for causing death with a knife, albeit a knife that was brought by the deceased himself, cannot be described as a harsh sentence.

"We acknowledge there were no aggravating features, which enabled the judge to pass a merciful sentence, and it is one which cannot be described as wrong in principle or manifestly excessive."