Global pharmaceutical firm Pfizer has reported a slip in profits amid mounting speculation it will try to bolster its business with a hostile bid for British firm AstraZeneca.

Pfizer, led by Scotsman Ian Read, 60, is struggling as the patents on many of its drugs gradually expire.

Yesterday the Viagra manufacturer revealed profits of $2.3bn (£1.4bn) for the first quarter of this year - down 15% on 12 months ago.

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As pressure mounts on the UK Government it is thought a hostile bid for AstraZeneca - which has 6700 UK staff and 51,000m worldwide - could be announced as early as today.

It could lead to calls for the potential takeover to be referred to the competition authorities.

Announcing the results Mr Read, chairman and chief executive of the US-based Pfizer, said: "I continue to see attractive opportunities to pursue profitable revenue expansion, both organically and through prudent business development."

Last week AstraZeneca rejected a £63 billion takeover offer from Pfizer, saying that it substantially undervalued the business.

At the weekend the proposal triggered a political row as Ed Miliband accused David Cameron of being a "cheerleader" for Pfizer.

He has written to the Prime Minister demanding a "stronger role by the UK Government" in the deal, which has the potential to create the world's biggest drugs company.

Mr Miliband said: "No other country in the world would be waving this bid through, nodding it through, on the basis of pretty weak assurances from Pfizer who have a pretty dubious record in this country and [with] other takeovers."

The Labour leader has also demanded a full assessment of the bid and is urging a review of the impact on Britain's pharmaceutical sector, science base and jobs.

Liberal Democrat Business Secretary Vince Cable has indicated he is sympathetic to those calls.

He is also considering reforms to the "public interest test" for corporate takeovers.

It follows a call last week from former Tory cabinet minister Lord Heseltine for ministers to have greater powers to block bids if they do not consider them to be in the public interest.

Mr Cable said that while the British competition and merger regime was non-political, "there is an important national interest here".

He said that he welcomed a letter last week from Mr Read to the Prime Minister promising to protect jobs at AstraZeneca in the UK for five years unless "circumstances significantly change".

Mr Cable said: "Obviously there is a lot of small print to study, the question about how these obligations are binding."

But he insisted that the UK Government was "strictly neutral" between the two companies.

Conservative Party chairman Grant Shapps hit back at Mr Miliband accusing the leader of "playing politics with people's jobs" and being "anti-business in every single way".

But he added: "We are going to have tests which ensure that this get-together becomes a great Anglo-American project or it doesn't happen."

Downing Street has said that it has made clear to Pfizer that its interest is in maintaining UK jobs.