Ed Miliband, the Labour leader, wrote to the Prime Minister to demand an independent review of the American giant’s £63 billion bid for AstraZeneca.

In the letter he argued for a “stronger role by the UK Government” arguing that Pfizer’s 50p-a-share offer for Astra, which was rejected on Friday, raised “serious questions about a key sector in our economy”.

The Mayor of London has also suggested that the deal should be subject to more searching scrutiny by the Government to ensure that investment in research and development and the bio technology industry was protected.

Mr Johnson said: “I don’t think politicians can be entirely aloof from this, and I think it would be very important to establish – I am not taking a position against the deal necessarily – but it would be very important to establish that Pfizer is genuinely committed to Rand D in this country.

Ian Read, chief executive of US-based Pfizer, last week wrote to Mr Cameron promising to keep AstraZeneca’s plans for its new Cambridge site, retain “substantial commercial manufacturing facilities” at Macclesfield and protect jobs for five years unless “circumstances significantly change.”

However concerns remain that Pfizer’s main motivation is to use the deal to move its tax domicile to the UK.

Mr Johnson suggested that while the deal was a “fantastic opportunity” it must be subject to a “test” ensuring any deal would not “in any way” damage Britain’s success in dominating the European scene in life sciences and bio technology.

Under the Enterprise Act, the Government can only intervene in deals involving defence or media companies. In 2008 an order was added to allow Lloyds TSB to buy HBOS in the interest of financial stability

Chuka Umunna, Labour’s shadow Business Secretary, has called for another category to be added to protect national interests in research & development which would include Pfizer’s bid.