Straw, who's son Will was a leading campaigner for Remain in the 2016 referendum, said "were we to stay in the EU it would have been easier to get united action out of the EU."
But Julia responded by asking "are you kidding me?
"The idea that our French and German allies would be more likely to stand up against the Russians attempting to assassinate people on British soil because we’re members of the EU, as opposed to because it’s the right thing to do, that’s quite a statement."
Straw argued "it’s how politics works" and "I voted remain but I’m under no illusion about the EU.
"In principle you’re right, that.. European allies should take action because it's the correct thing to do, but in the real world if you're in an alliance it makes life much easier."