ASTRAZENECA has rejected a £63bn takeover offer from US rival Pfizer, claiming it substantially undervalues the business.

The company turned down the bid from the Viagra maker hours after Pfizer stepped up its pursuit by making the increased offer and pledging the future of UK jobs and research.

At £50 a share, the offer represented a 7 per cent increase on a previous proposal in January.

However, an AstraZeneca spokesman said: “The financial and other terms described in the proposal are inadequate, substantially undervalue AstraZeneca and are not a basis on which to engage with Pfizer.”

AstraZeneca has plants in London, Cheshire and Bristol.