Kathryn Smith (pictured) was left with a two centimetre stab wound on her cheek after being jumped by as many as 10 lags on a prison stairwell in May

A drug addict who stamped her 21-month-old daughter to death is appealing against her conviction for murder.

Smith was jailed for life in April with a minimum of 24 years.

Her ex-partner, Matthew Rigby, 22, was convicted of causing or allowing the child's death, but cleared of murder.

Ayeeshia, who weighed just 20lbs when she died, was killed while she cried 'stop mummy, stop daddy'.

Her mother stamped on her chest with such force that she suffered a fatal heart injury, three broken ribs and bit through her own tongue.

Experts said her injuries were so severe she resembled a high-speed car crash victim.

Smith, from Swadlincote, Derbyshire, today challenged her conviction at the Court of Appeal in London.

Ayeeshia Jane Smith (pictured), who weighed just 20lbs when she died, was killed as she cried 'stop mummy, stop daddy'. Her mother stamped on her chest with such force that she suffered a fatal heart injury, three broken ribs and bit through her own tongue

Her barrister, John Butterfield QC, argued her conviction was 'unsafe' because of an interruption by the trial judge during the defence's closing speech.

Mr Butterfield, who represented Smith at the trial, said Mrs Justice Andrews' intervention caused 'prejudice' in the minds of jurors.

He said: 'The judge weighed in and weighed in in a way that was wrong, I say, on a number of different levels, in the middle of defence counsel's closing address.

'It is hard to understate just how devastating this was to the credibility of the defence case.

'To trespass on the closing remarks at all was a risk and was likely to have consequences.'

But Christopher Hotten QC, who prosecuted her, denied the judge’s interruption rendered the conviction unsafe.

The Lord Chief Justice, Lord Thomas, sitting with Mr Justice Wyn Williams and Mr Justice Goss, are expected to give a ruling in the New Year.

But Lord Thomas said if her conviction appeal does not succeed they would review the minimum jail term handed to Smith.

Smith was attacked by fellow inmates at the notorious Foston Hall women's prison in Derbyshire in May. The mob claimed they were avenging Ayeeshia's death.