The state visit will go ahead despite concerns raised after a gunman targeted an event attended by the president.
The Conservatives say the PM misled Parliament "multiple times" and that the Privileges Committee should investigate.
Poor housing, obesity and the effects of deprivation have been suggested as underlying cause.
British families tell BBC Panorama how the Iran war is affecting their monthly budgets.
Chief Constable Jon Boutcher says his officers suspect the bombing was carried out by the dissident republican group known as the New IRA.