The fun and games in Parliament over Pfizer's proposed takeover of AstraZeneca has kicked off with an edgy session between the US drug giant and MPs.

Chief executive Ian Read has been talking to the Commons Business, Innovation and Skills select committee and has failed to convince the panel about its commitment to the UK if it succeeds in getting hold of AstraZeneca. Committee chairman Adrian Bailey began the hearing by referring to quotes made this week  that Pfizer is '"a praying mantis" and "a shark that needs feeding", which Mr Read dismissed, saying the company has "high integrity".

However Mr Read suffered something of a wobble when asked about R&D. Having committed to keeping 20% of researchers in the UK, he could not give any figures as to how many that would be, nor could he give any numbers about a geographic breakdown of Pfizer's present R&D expenditure.

He was repeatedly asked about how many people would be employed by AstraZeneca in R&D if the Pfizer takeover bid succeeds. Mr Read said he cannot make specific commitments because he has not had any serious contact with AstraZeneca yet, adding that as "a man of my word", he is happy to make a substantial commitment "sight unseen".

However, Mr Read admitted that a combined company would have a lower R&D budget, inevitable given issues of duplication of pipeline projects. He added that it would be irresponsible to make promises about job cuts but spoke of its five-year commitments over jobs as "unprecedented".

Chief financial officer Frank De'Amelio acknowledged that the tax benefits in the UK, saying that Pfizer pays about 27% now, which would be "clearly less".  He went on to say that if there were no tax advantage, the price being offered would change.

There will be more from the Committee later today including the contributions from AstraZeneca CEO Pascal Soriot who has just starting giving evidence.