Most of the violence against UK forces in Basra is being engineered by Iranian elements, a British Army colonel based in the southern Iraqi city says.
Weapons used against troops were coming from Iran, the colonel said
Col Justin Masherevski told BBC News that Iran was providing "sophisticated weaponry" to insurgents.
"Iranian agents" were also paying local men to attack British troops, he added.
PM Tony Blair has previously said weapons used were of "Iranian origin". The Ministry of Defence (MoD) says any Iranian links are "unacceptable".
Tehran has repeatedly denied that it is fuelling the violence in Iraq.
Col Masherevski said "local information" indicated that "the vast majority of the violence against us is inspired from outside Iraq".
"The people here very much believe that is Iran," he said.
"All the circumstantial evidence points to Iranian involvement in the violence here in Basra which is disrupting the city to a great extent."
The standard of weapons being used against British troops was such that it could only have come from outside Iraq, he said.
"These are not old munitions being used from the Iran-Iraq war, they're much more modern - some of them produced in 2006.
"The locals are telling us these are coming in from Iran."
And it was believed Iranian agents were paying "up to $500 a month for young Baswari men to attack us", he added.
An MoD spokesman said: "Any Iranian links to armed groups in Iraq outside the political process, either through supply of weapons, training or funding are unacceptable.
"These undermine Iran's long-term interest in a secure, stable and democratic Iraq."
Last month Mr Blair, answering a Commons question about Iraq, said it was "perfectly obvious... that ordnance, much of which was used against British soldiers, has an Iranian origin.
"No-one can be sure of the precise degree to which those in the senior levels of the Iranian government are complicit but it is certainly very clear that is the origin of the weaponry," he added.
The question was prompted by US President George Bush's assertion a week earlier that a branch of Iran's Revolutionary Guards was linked to some attacks on US troops in Iraq.
He said the US was "certain" that the force was providing a weapon known as an EFP which had been used in particularly deadly attacks.
He did not know who was directing the force , he added.