Defence Secretary Des Browne today asked the High Court to outlaw the use of language strongly critical of the MoD in inquest verdicts on soldiers who have died on active service.

The application came in a test case relating to Territorial Army soldier Pte Jason Smith, who died of heatstroke in Iraq.

Oxfordshire's assistant deputy coroner, Andrew Walker, recorded in a November 2006 inquest verdict that Pte Smith's death was "caused by a serious failure to recognise and take appropriate steps to address the difficulty that he had in adjusting to the climate".

The 32-year-old fell ill in temperatures of 60C (140F) in August 2003 at the Al Amara stadium, southern Iraq.

The coroner's narrative verdict described how he was taken to the medical centre at Abu Naji Camp, where he died.

The coroner said Pte Smith's difficulty in acclimatising to the heat should have been recognised.

The wording of his verdict came under attack at the High Court in London today before Mr Justice Collins.

Sarah Moore, appearing for the Defence Secretary, said the coroner should not have made reference to a "serious failure" to take appropriate steps.

The use of the phrase could be seen as deciding civil liability for Pte Smith's death, and that was not allowed under Rule 42 of the 1984 Coroners' Rules, she argued.

Lawyers acting for the late soldier's mother, Mrs Catherine Smith, from Roxburghshire in Scotland, argue the Defence Secretary's legal challenge was "misconceived".

The judge was told the issue remained important as a new inquest was to be held into Pte Smith's death because of flaws in the original hearing.

Ms Moore said "a matter of general importance" had been raised because the phrase "serious failing" was cropping up on a regular basis in inquests into Iraqi military deaths.

Pte Smith's family are also making submissions to the court over the scope of the new inquest and asking the judge to order full disclosure of MoD documents, save those covered by public interest immunity.

Wiltshire Coroner David Masters, currently tasked with conducting inquests into many of the deaths of British servicemen in Iraq and Afghanistan, said: "I am unable to make any comment on this particular case.

"Having said that, I do not consider that this will deflect coroners from conducting full, frank and fearless inquiries into the deaths that they are entrusted to investigate - those of people serving their country when they are killed abroad.

"If something needs to be said, I'll say it."

Geoff Webb, coroner's officer for Andrew Walker, said Mr Walker felt it would be inappropriate for him to comment.