The Portsmouth North MP made the admission yesterday before a defence select committee inquiry into the Gulf shipping crisis.
Ms Mordaunt demanded an ‘audit trail’ in mid-June after three verbal requests for a Cobra meeting with ministers were ‘not acted on’.
She told the committee she then wrote formally to then-prime minister Mrs May, calling for a meeting which would get ministers together to ‘thrash out’ issues of politics and security in the region.
This plea was again rebuffed, even after Ms Mordaunt warned the UK was ‘very likely to be facing having a ship taken’.
An official reply on June 27 said: ‘The decision to call a ministerial Cobra is for the PM. Events to date have not been judged to warrant this.’
It was only after Ms Mordaunt sent a second formal letter to Mrs May, on that day, that a meeting was finally planned for July 10.
It came six days after an Iranian oil tanker, Grace 1, was seized by Royal Marines as it passed through Gibraltar and nine days before the British-flagged ship Stena Impero was taken by Iran.
Iran has now hinted it could release the tanker ‘within days’.
Warship HMS Kent left Portsmouth for the Strait of Hormuz – where the Stena Impero was seized – last month.