The company's pledges on U.K. jobs are "unprecedented and incredible," Read argued.
Read claimed that the company did not make similar promises in the case of Swedish company Pharmacia, which has frequently been cited as an example of the U.S. giant retreating on its pledges to keep jobs. He challenged MPs to prove whether Pfizer was lying in this instance.
Read MorePfizer/AstraZeneca: The numbers you need to watch
One of the reasons Pfizer's approach to AstraZeneca is viewed with such cynicism is because of the tax advantages to the company of such a deal. The "tax inversion" practice means that, if Pfizer spends its overseas cash on a foreign company rather than paying tax on it in the U.S., it can headquarter the merged company abroad, as long as the smaller company represents at least 20 percent of the combined company. There are concerns that, if tax is the main motivation, investment inresearch and development, and U.K. jobs, will be far down Pfizer's priority list.
Read MoreA deal to dodge the taxman
The prospect of the tax advantages of buying AstraZeneca being damaged by U.S. government intervention seem to have receded, after Orrin Hatch, a senior Republican Senator on the Senate finance committee, said "confusing and arbitrary retroactive restrictions on U.S. companies" would not solve the problem of "tax inversion."