With fears growing that British jobs will be lost and the nation's science base undermined in the potential merger, Prime Minister David Cameron denied in a BBC interview today that he was favouring the American company.
When asked on The Andrew Marr Show whether he was engaging more closely with Pfizer, Cameron insisted that was not the case.
Cameron said "ministers were talking to AstraZeneca before anyone spoke to Pfizer."
Pfizer has been trying to buy AstraZeneca since January, but has been rebuffed three times. The proposed deal would be the largest foreign takeover of a British company.