The UK has signalled it wanted more guarantees from Pfizer, the US drug firm seeking to acquire AstraZeneca, and held open the possibility of blocking the deal using a “public interest” defence.

Prime Minister David Cameron reiterated that he wanted “more” from the firm, while his deputy Nick Clegg said he wanted “exacting, binding commitments” rather then “aspirations”. Their comments came after Pfizer advanced its charm offensive on Saturday with a series of videos extolling the scientific benefits, while downplaying potential tax advantages.

“I’ll always stand up for British jobs, British interests, British science, British R&D,” Cameron said in a BBC television interview. “The business secretary is looking at this issue of public interest defence and he will report back to parliament.”

Clegg said in an interview with Sky News: “Bitter experience in other contexts has taught us about the importance of pinning these commitments down and not just allowing them to rest as aspirations but to make sure they are exacting, binding commitments. There are ways they could be made more solid and that’s [what] we’re discussing with Pfizer.”

Business Secretary Vince Cable’s examination of how the proposed takeover could be blocked on public interest grounds included the possibility of referring the case to the European Commission or proposing a change to the Enterprise Act that would widen the public-interest test for takeovers, a person familiar with discussions in government said.

The Labour Party called for a “stronger public-interest test” to be applied. – Bloomberg