Saddam Hussein was hanged in northern Baghdad on Saturday

Malcolm Smart, of Amnesty International, said the death penalty "in all cases was a violation of the right to life".

Human Rights Watch's Tom Porteous said justice had "suffered a cruel blow" because of the "inhumane punishment".

Capital punishment in the UK was suspended indefinitely in 1969.

It is even more worrying that in this case the execution appeared a foregone conclusion once the original verdict was pronounced Malcolm Smart Amnesty International Saddam 'held to account' Iraqi Kurds react to execution World views on death penalty

Mr Smart said the death penalty was "the ultimate cruel, inhuman and degrading punishment".

"It is even more worrying that in this case the execution appeared a foregone conclusion once the original verdict was pronounced," he added.

Saddam Hussein was hanged for crimes against humanity.

Mr Porteous, the London director of Human Rights Watch, told BBC News: "The very important thing to say is that this is a day when justice has really suffered a cruel blow.

"This is an inhuman punishment - a hasty punishment - which comes after a deeply flawed trial and after an even more flawed appeals process."

'Shed tears'

Manzoor Moghal, chairman of the Federation of Muslim Organisations in the UK said two wrongs did not make a right.

Saddam was brutal, dictatorial and unjust but that does not give his executors the right to be slightly less brutal, slightly less dictatorial and not quite as unjust Federation of Muslim Organisations

"Nobody must shed tears for Saddam Hussein as a person but they must shed tears for what has now happened to Iraq as a country and for its people," he said.

"Saddam was brutal, dictatorial and unjust but that does not give his executors the right to be slightly less brutal, slightly less dictatorial and not quite as unjust."

And Dashty Jamal, of the UK-based International Federation of Iraqi Refugees, said the organisation was "against the death penalty anywhere else in the world".

A6 murder

In 1969, Parliament voted to suspend the death penalty indefinitely.

Notorious killer James Hanratty, 25, was one of the last people to be executed before its abolition.

He went to the gallows on 4 April 1962 after he was convicted of the notorious A6 murder in Bedfordshire in which scientist Michael Gregsten, 36, was shot dead.

A mandatory life sentence was introduced in place of the death penalty.

Repeated calls for its return have been consistently rejected.

James Hanratty was hanged after his conviction for the A6 murder

In 2002, Tory former Home Office minister Ann Widdecombe - then MP for Maidstone and the Weald MP - said the death penalty should be "available" to the UK justice system for the most heinous of crimes.

She was speaking following the murders of schoolgirls Holly Wells and Jessica Chapman in Soham, Cambridgeshire.

Last year, former Met Police head Lord Stevens called for the death penalty to be reinstated for those who kill police officers.

Opinion polls have repeatedly suggested that a significant percentage of the UK population was in favour of capital punishment being reintroduced for certain crimes.

A survey carried out by pollsters Mori in January suggested that more than half of the readers of the Sun newspaper were in favour of the death penalty for child killers and terrorists.

But despite these results, the issue of the death penalty has not featured on the political agenda in recent years.