The mother of a soldier killed in Iraq while driving in a poorly protected Snatch Land Rover has begun an unprecedented legal action against the Ministry of Defence.

Susan Smith is suing for negligence and a breach of her son's human rights after she claims he was sent out in a vehicle which had no chance of protecting him from the well-known threat of booby-trap roadside bombs.

Private Phillip Hewett, 21, from Tamworth, was serving in the 1st Battalion Staffordshire Regiment in the hotbed Iraqi town of Al Amarah when his patrol of three Snatch Land Rovers was hit by a huge roadside bomb in 2005.

British soldiers on patrol in Iraq

His colleagues Private Leon Spicer and 2nd Lt Richard Shearer were also killed.

The landmark case marks a crucial test of the MoD's traditional legal defence of Combat Immunity, used to block any court challenges arising from events on foreign battlefields.

Recent court rulings have undermined that principle and the latest case, if successful, could lead to dozens more claims from families of dead servicemen blaming their deaths on inadequate or missing equipment.

The Snatch vehicle was designed for use in Northern Ireland 20 years ago and offers little protection against roadside bombs or rocket-propelled grenades - both weapons of choice for Iraqi insurgents.

Dozens of soldiers are thought to have been killed while patrolling in Snatch Land Rovers, which are still in use in Iraq and Afghanistan.

Four soldiers were killed in a Snatch in Afghanistan in June, including Corporal Sarah Bryant, the first British woman killed in the conflict.

Though the MoD is spending hundreds of millions of pounds on new armoured vehicles, officials insist there is still a role for the Snatch.

Mrs Smith yesterday served a detailed statement of her claim on the MoD.

Her lawyers said the case would turn partly on whether the MoD's combat immunity extended to crucial decisions made by senior commanders and officials in advance, back in the UK.

Jocelyn Cockburn, a partner at Hodge Jones & Allen, said: 'The use of Snatch Land Rovers in Iraq was not something decided on the battlefield on the day. It was decided as a matter of policy back in Britain.'

The claim accuses the MoD of an 'unacceptable delay' in buying heavier armoured vehicles for use on patrol, and a 'failure to recognise that Snatch were unsuitable for the extremely dangerous conditions in Iraq'.

Mrs Smith's lawyers will also argue that the department breached Private Hewett's human rights, namely his right to life. In May this year, the High Court ruled that the Human Rights Act could offer some legal protection to British soldiers 'wherever they may be'.

She said: 'Susan Smith had campaigned tirelessly, along with others, to bring these safety concerns to the public attention and to try and persuade the Government to stop sending soldiers out in Snatch Land Rovers.

'Unfortunately, deaths are still occurring in these vehicles.

Mrs Smith's legal team is preparing other similar cases involving deaths in Snatch vehicles including that of Irish Guardsman Lance Corporal Kirk Redpath, 22, who was killed outside Basra in August 2007.

 - Britain lost another soldier in Afghanistan yesterday, the 116th to die there. The unnamed member of the 2nd Battalion the Royal Regiment of Scotland was part of a patrol hit by an 'improvised explosive device' in Helmand.