The most antisemitic member of the UK House of Commons almost certainly isn't Jeremy Corbyn.
It's Chris Williamson.*
Basically, if there is an antisemite on the left, Williamson has been there to defend them.
When Jackie Walker -- currently suspended from Labour after (among other things) accusing Jews of being the primary backers of the slave trade, complaining that Holocaust Memorial Day is too Jew-oriented, and challenging the need for heightened security at Jewish schools and synagogues as the product of exaggerated and embellished fears -- sought a venue to host her new film "Witchhunt" (guess who the witch-hunters are?), Williamson happily offered to give her a room in parliament -- a decision the Board of Deputies of British Jews likened to an act of "trolling".
When Ken Livingstone -- who said that Hitler was a "Zionist" -- was suspended from the Party, Williamson was manning the ramparts demanding that he (and Walker) be let right back in.
When Jewish Labour MP Ruth Smeeth was accused by Marc Wadsworth of being a right-wing operative because she was challenging antisemitism in her party, Williamson accused Smeeth and her backers of being the faces of "White privilege" (Wadsworth was eventually expelled from Labour).
When people were organizing to deplatform vicious antisemitic musician Gilad Atzmon, Williamson signed a petition ... defending Atzmon and urging that he be permitting to perform (Williamson did apologize for that one, saying that he -- somehow -- didn't know of Atzmon's antisemitic record, despite that being the only reason he's of any public prominence at all).
Williamson has said that he's "never seen antisemitism in the Labour Party," -- a fascinating argument coming from someone who's twice had to apologize for his own antisemitic dalliances. Perhaps he doesn't own a mirror?
But today, finally, Chris Williamson was suspended from Labour after telling a cheering crowd that his party -- which just saw a mass exodus of members prompted in part by worries of institutional antisemitism -- had been "too apologetic" about antisemitism.
Apparently, the suspension occurred only after an intervention by Corbyn himself. Not to facilitate the suspension to show that Labour was done soft-playing antisemitism in its upper ranks. Rather, Corbyn was trying to shield Williamson from consequences for his actions -- perhaps not surprisingly, since he's naturally one of Corbyn's most vocal allies in the party.
A massive blowback from within the Labour Party forced Corbyn to back off. And so, for now, Chris Williamson is under suspension.
* Incidentally, the most antisemitic member of the UK legislature is not a Labour member. That would have to be Baroness Jenny Tonge, formerly of the Liberal Democratic Party (though she was suspended and eventually resigned under a cloud of her own antisemitism controversies).