The board of US drugs giant Pfizer has approved its $150 billion (£100bn) bid for Botox manufacturer Allergan.

If the deal goes ahead, it will be the biggest in pharmaceuticals history and will create the world's largest pharmaceuticals company.

Pfizer last year failed in its attempts to acquire UK rival AstraZeneca. But its bid was rejected, with the British firm claiming the offer massively undervalued the company. It is understood that Pfizer wants to relocate its headquarters out of the US to avoid relatively high corporate tax rates.

Pfizer chief executive Ian Read would lead the merged company, with Allergan boss Brent Saunders as his deputy.