Iraq is now in a "worse shape" than it was under Saddam Hussein, with millions living without even the most basic medical care or access to clean water.

This is despite five years of military operations which have cost hundreds of thousands of Iraqi lives, 135 British personnel killed and £6.4bn of taxpayers' money.

The grim picture emerged as the International Committee of the Red Cross (ICRC) published a report warning that Iraqi hospitals were still lacking beds, drugs and medical staff, while the poor public water supply has forced some families to use at least one-third of their average monthly income buying clean drinking water.

"Five years after the outbreak of the war in Iraq, the humanitarian situation in most of the country remains among the most critical in the world," it said, describing Iraq's healthcare system as "now in worse shape than ever".

It warned that those who had fled their homes during the conflict remained extremely vulnerable.

"Better security in some parts of Iraq must not distract attention from the continuing plight of millions of people who have essentially been left to their own devices," said Beatrice Megevand Roggo, the ICRC's head of operations for the Middle East and Africa.

Tony Blair's former chief of staff, Jonathan Powell, acknowledged yesterday the UK Government did not plan adequately for the aftermath of the war in Iraq and it could take decades for the situation in the stricken country to become settled.

Mr Powell, who worked for former prime minister Mr Blair for 10 years, said: "We probably hadn't thought through the magnitude of what we were taking on in Iraq. This is something that will take many decades to sort itself out."

Opposition politicians renewed calls for an "early and full" withdrawal of British troops from Iraq, ahead of the fifth anniversary on Thursday.

Liberal Democrat leader Nick Clegg said: "Never again should the objections of millions of British citizens be so lightly ignored."

Analysis by The Herald shows Scots make up one in six of all British soldiers' deaths during the war, even though they account for about 10% of manpower across the Army and 8% of the UK population. The units which now make up the five-battalion Royal Regiment of Scotland (RRS) have also suffered more deaths than any other UK infantry regiment, with the Black Watch (now 3rd battalion, RRS) hardest hit.

A breakdown of casualties shows that while 135 British servicemen and women have been killed in action or as a result of wounds sustained in action, 99 have been in the Army and the others were from the Royal Navy, Royal Marines and RAF. From the Army's battlefield toll, 16 are Scots.

By contrast, only four Scots soldiers have been killed by the Taliban in Afghanistan, 6.3% of the 63 UK service personnel to die in action there since 2001. Two other Scots, one from the RAF and a Royal Marine, have also died in Helmand.

One officer with experience of several tours in Iraq said yesterday: "The Black Watch were deployed for the initial invasion of Iraq and then the subsequent support operation near Falluja because they were one of the most experienced Warrior armoured infantry units in the Army.

"If you're in the front line, you will inevitably risk taking more casualties."