While he and defence secretary John Healey wanted to let America use British bases at the outset of the war, he was effectively blocked by Rachel Reeves, Yvette Cooper, Shabana Mahmood and, most vociferously, Ed Miliband.
Article source: https://www.huffingtonpost.co.uk/entry/why-war-in-iran-is-the-last-thing-keir-starmer-needs_uk_69a95e86e4b0a6593a333eba