The Prime Minister feels Labour MP Austin Mitchell was "quite wrong" to liken Pfizer to "rapists" in a Twitter post, his official spokesman has told reporters.
Asked if David Cameron thought Mr Mitchell should be disciplined by his party, the spokesman said, "He does think this is something for the Labour Party."
Mr Mitchell's original tweet also suggested Mr Cameron "dare not stop Pfizer because he dare not offend the US in any way".
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The operation to recover the unexploded bomb near the Houses of Parliament let to disruption in central London overnight.
Southern parts of England and Wales will see sunny skies after a frosty start.
A police spokesman said the incident in the Bourke Street Mall on Friday was not related to terrorism.