Former leaders of the armed forces have raised fears that the morale of troops in Iraq is being damaged by the number of criminal investigations they face.
The forces chiefs stress the importance of the chain of command
Six ex-chiefs of the defence staff criticised ministers in the House of Lords on Thursday.
Field Marshall Lord Bramall, former chief of Defence Staff, told peers attention should be paid to "realities on the ground".
The Ministry of Defence says the number of troops prosecuted is very small.
Speaking during the debate Lord Bramall said soldiers had to make "on the spot" judgements on whether or not to open fire "to safeguard his own life and that of his comrades".
This judgement, he said, "should only be reviewed, justified, condemned if further investigation becomes necessary, by those familiar with similar situations and aware of the environment and pressures prevailing at the time".
Lord Boyce, who was chief of defence at the time of the Iraq War, said the "unique linkage" between the commanding officer and his men should be left alone.
"If that is destroyed the consequences could be serious," he said.
Lord Boyce earlier told BBC News that the armed forces were left with "no confidence" that they would be dealt with by their peers "who understand the nature of operational circumstances", he said.
"There is serious shock among the rank and file ... when they are busy fighting on the ground," he added.
There are 70,000 British troops in Iraq and since the start of the Iraq war there have been 176 investigations, says the MoD. Of those, 151 have closed without action.
Some of the fears were sparked by the case of Trooper Kevin Williams, who was accused of murder in Iraq before the charges were dropped nearly two years later.
Trooper Williams was arrested and charged with murder on 7 September 2004, following an investigation by Scotland Yard detectives requested by the attorney general.
He had shot a man after a fracas in the private courtyard of a house not far from the southern Iraqi city of Basra.
The case had previously been dismissed by Trooper Williams' commanding officer, which meant he could not be tried by a military court martial.
Some of the ex-forces chiefs are worried about the length of the investigation.
They say there is a perception, rightly or wrongly, that it took a retired general to protect Trooper Williams' interests.
Crossbencher General the Lord Guthrie of Craigiebank, Chief of the Defence Staff in 1997-2001, said on Thursday he wanted assurances that British service personnel would not be sent to the International Criminal Court - a worry shared by many of the ex-chiefs.
He added: "Can the Government give serious consideration for the British armed services to opt out - like the French forces - from our commitment to the European Convention on Human Rights?"
Ministers say it would take a "catastrophic failure" for British troops to be prosecuted by the International Criminal Court for "war crimes".
Junior Defence Minister Lord Drayson, rejected the fears that British soldiers would find themselves in the dock in the Hague, whether Britain liked it or not.
He told the Lords: "We are absolutely clear about the essential nature of a commanding officer to exercise discipline in respect of those under his command, but the system must be fair, efficient and compliant with the European Convention."
He said the Armed Forces Bill, which the government wants to introduce later his year, would underline its commitment to a system of service law.
Talking earlier on BBC Radio 4's World at One programme, Phil Shiner - who leads a group called Public Interest lawyers and has been acting in relation to the conduct of British troops in post-war Iraq - said the armed forces could not be trusted to administer their own system of justice.
"Everything that we know - and that the attorney general knows - shows us that the military are completely incapable of investigating and prosecuting themselves," he said.