Barry Gardiner recalled Boris Johnson telling a TV audience there were no US-UK talks about drug price negotiations.
The Labour front bencher said there had been six meetings between officials about wording for a future trade deal.
Andrew Neil asked him for evidence Britain had agreed to give the US access to UK markets.
The front bencher said: “If ministers are allowing civil servants to go off and negotiate this, either they are in control of it, in which [case] they know what is going on, or they are not in control of it.”
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