Tony Blair presented evidence about Saddam Hussein's weapons of mass destruction "with a certainty that was not justified", a long-awaited report into the Iraq War has concluded.
Setting out the findings of his inquiry, Sir John Chilcot said the then prime minister committed British troops to the 2003 invasion before the peaceful options for Iraq's disarmament had been exhausted.
Sir John also hit out at the lack of proper planning for the period after the fall of Saddam, which saw British troops involved in a prolonged and bloody occupation.
The former Whitehall mandarin was setting out the findings of his inquiry into the UK's most controversial military engagement since the end of the Second World War.
Presenting a summary of the 2.6 million-word report, he said: "We have concluded that the UK chose to join the invasion of Iraq before the peaceful options for disarmament had been exhausted.
"Military action at that time was not a last resort."
The inquiry panel also found:
:: Despite explicit warnings, the consequences of the invasion were under-estimated;
:: Planning and preparations for Iraq after Saddam's fall were "wholly inadequate";
:: Mr Blair's government failed to achieve its stated objectives.
Sir John said taking part in the US-led invasion of Iraq was "a decision of the utmost gravity" but acknowledged that Saddam "was undoubtedly a brutal dictator who had attacked Iraq's neighbours, repressed and killed many of his own people and was in violation of obligations imposed by the UN Security Council".