Laura Murray, a political adviser to the Shadow Cabinet, made the startling charge on social media after the President launched missiles at air bases in Syria in retaliation of an alleged weapons attack.
She wrote: “Apparently killing children is fine as long as it is America doing it.”
Her message – the account from which appears now to have been deleted – was written in response to news reports claiming the strikes had killed civilians in Syria.
But Labour officials reportedly reacted angrily to the tweet, and claimed it was an example of why their party is unable to resonate with the public.
A Labour source told the Mail on Sunday: “This is exactly the sort of peacenik, puerile rubbish which explains why the party is so unpopular.”
Laura Murray made the accusation after Trump's decision to strike Syrian air bases
Trump described the weapons attack as "unspeakable"
The Labour leader found himself at odds with his party by denouncing the air strikes on Friday.
Many Labour MPs, including deputy leader Tom Watson, backed the President’s response to the chemical attack.
A Syrian refugee spoke out about how he was “silenced” by a protest led by the Stop The War Coalition outside Downing Street when he tried to defend Trump’s decision.
Corbyn denounced the strikes, putting himself at odds with his party Celebrities and Politicians React to Trump's Missile Attack on Syria Fri, April 7, 2017
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Following news of the attack, celebrities and politicians expressed their thoughts on social media
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Trump ordered a massive military strike against a Syria
Hassan Akkad, 29, fled Syria after being tortured by president Assad’s military.
He asked the left-wing group’s rally on Friday evening if he could use their megaphone to say something.
When the group refused, he shouted that Trump’s decision to bomb the air base was a good thing, because Assad was using it to kill civilians.