British investigators say 131 people were potentially exposed to the chemical used in Salisbury on March 4th.
Former Russian spy Sergei Skripal and his daughter remain in a critical condition after the attack.
The UK says Russia is culpable and is expelling 23 diplomats.
Moscow denies involvement.
Labour MP Hillary Benn says the UK response should be robust as investigations continue.
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http://www.fsnradionews.com/feeds/0316russia-benn1.mp3