There is "no question" of British troops being sent back to Iraq to help the country deal with Islamist extremists who have seized control of key cities, William Hague has said.
The Foreign Secretary said the situation was of great concern but that the Government was "not countenancing at this stage any British military involvement" and believed Baghdad had sufficient domestic forces to counter the threat.
Iraqi Prime Minister Nouri al-Maliki has appealed for help from the international community after militant fighters seized control of the country's second largest city Mosul earlier this week.
The fighters – who yesterday were reported to also have control of Saddam Hussein's home city of Tikrit – are believed to be affiliated with the Islamic State of Iraq and the Levant, an al-Qaida splinter group that is one of the most ruthless rebel organisations both in Iraq and across the border in Syria.
Urging Iraq's political leaders to swiftly end the deadlock over the creation of a new coalition government, Mr Hague (below) said the insurgency was evidence of the Syrian civil war "infecting" the region.
But he dismissed suggestions that the 2003 US-led invasion to topple Hussein had left Iraq more vulnerable to such insurgencies.
"We are very worried about this," he said.
"It's very important that the civilian population are protected as well as possible, that people who are fleeing the area are looked after by the Iraqi authorities and people in neighbouring countries as well."
Mr Hague dismissed suggestions that the UK had a duty to intervene because of its previous role in the Iraq war.
"You can't say the crisis was created by invading it and then we should invade it again," he said. "I don't think that's part of the solution."
The insurgents expanded their offensive yesterday closer to the Iraqi capital as soldiers and security forces abandoned their posts following clashes.
An estimated half a million residents have fled Mosul. Iraqi foreign minister Hoshyar Zebari said leaders must work together and deal with the "serious, mortal threat" facing Iraq.