AstraZeneca's share price tumbled by a double-digit margin on the London stock exchange after it was revealed the UK drugmaker had rejected Pfizer's latest offer - which the US pharmaceutical giant called its last - to acquire the company.

The share price had risen steadily in the weeks since the first takeover offer was launched.

On May 18, Pfizer said it was prepared to pay £55 ($92.50) per share, valuing the UK company at £69 billion. However, the AstraZeneca board of directors said that, after weekend discussions with Pfizer's management, it had voted to reject the latest bid.

Chairman Leif Johansson said he had made clear that the board could only recommend a bid more than 10% above an offer of £53.50 made by Pfizer on May 16. He blamed the US company for calling a halt to discussions after a more than one hour telephone call with Pfizer CEO Ian Read on May 18.

In addition to the inadequate price, Johansson also slammed what he said was a lack of industrial logic behind Pfizer's move, the risks posed to shareholders by the controversial tax plans and the threat to life science jobs in Britain, Sweden and the US.

The chairman added that the US group's pursuit "appears to have been fundamentally driven by the corporate financial benefits to its shareholders of cost savings and tax minimization."

Johannson told the news agency Reuters he now sees no prospect of a deal with Pfizer before a deadline of May 26 set under British takeover rules, or any likelihood of that deadline being extended.

Pfizer's proposal will expire at 5 p.m. UK time on May 26. After that, the company would have to wait six months before making another bid.

A merger of the two pharma players of unequal size would create the world's biggest drugmaker. It would be the largest-ever foreign acquisition of a British company, and has been opposed by many scientists and politicians who fear it would undermine the country's science base.