According to defence sources, Iran’s Revolutionary Guard trains bomb-makers in Iran and Lebanon who go to Basra to kill and teach others to do the same.
If the allegations are true, then Iran’s government, which has denied involvement, must be implicated, BBC defence correspondent Paul Wood says.
A British official said last week Iran had supplied bombs used in the attacks.
Our correspondent says bomb-making know-how is spreading, as one man can train 10 others.
Tony Blair expressed his concern last week over suggestions of an Iranian link.
He said evidence led either to Iran or its Lebanese militant allies Hezbollah, although “we can’t be sure of this”.
He warned Iran that there could be “no justification” for interfering in Iraq.
Iran has denied any role in the blasts that have killed eight British soldiers in Iraq in the last five months.
