Hillary Clinton and Donald Trump slam Pfizer-Allergan deal

Under the agreement, Dublin-based Allergan, the smaller of the two companies, would purchase York-based Pfizer, according to individuals briefed on the matter.

While Noonan said Allergan and Pfizer were plainly merging for "tax advantages", the government has no problem with the deal as both companies had "substantial" operations in Ireland. Pfizer, with revenue of $49.6 billion past year, employs 78,300 worldwide.

The US corporate tax rate of 35% is one of the highest in the world, and compares with Ireland's rate of 12.5%. The deal looks set to go ahead despite US Treasury opposition and the introduction of new rules created to prevent tax inversion where a company relocates its legal domicile to a lower tax nation.

As the race for the White House hots up, such so-called tax inversions have again raised the hackles of U.S. lawmakers.

If these figures are to be believed, then Ireland's coffers are about to be significantly boosted, considering last year's entire corporate tax revenues were €4.6bn.

The steps were "limited in scope and should have a fairly modest impact", Goldman Sachs Group Inc. analyst Alec Phillips said in a note to clients when the Treasury announced its measures.

Pfizer chief executive Ian Read will be CEO of the combined company, while Allergan CEO Brent Saunders will be chief operating officer, the companies said yesterday. "It's basically a tax inversion strategy, and certainly the benefits won't be passed on to consumers", Ando said.

"Washington is gridlocked", said Republican front runner Donald Trump, who has called for a corporate tax overhaul. When the acquisition is complete, Allergan shareholders will receive a total of 11.3 shares of the combined company per owned share while Pfizer shareholders will received 1 share of the combined company per owned share.

The board of directors for Allergan, the company best known for manufacturing Botox, has unanimously approved Pfizer's $160 billion merger proposal, according to a press release. The merger also comes as many big advertisers rethink their marketing budgets, slashing the number of agencies they work with and putting pressure on agency fees.

"We can rail all we want about how unpatriotic it is and how angry we are that Pfizer is selling to another company and they're going to move outside of America", Rubio said. "It's a great deal for the United States, given that it frees up our ability to invest in American science".

The alternative, he said, was to push for tax reforms to ensure corporations stay in the US.

They were also disappointed, analysts said, because Pfizer executives pushed back the timeline for making a decision by two years, saying it wanted to first focus on properly digesting Allergan.

The other, with a potentially mid-single-digit growth rate, would consist of older drugs that have lost patent protection or are about to, such as Pfizer's Celebrex arthritis drug and Allergan's Teflaro antibiotic.

The Wall Street Journal reported on Tuesday that Pfizer, which has always been considering splitting divisions within the company into two separate entities, were now intending to split the bigger, combined business in 2018.

"The fact that Pfizer is leaving our country with a tremendous loss of jobs is ", he said in a statement to Business Insider.

More than 50 similar deals have been done over three decades by well-known companies such as Medtronic Plc (Xetra: - news), Fruit of the Loom and Ingersoll-Rand Plc.

"It will also reduce the cash that could be used for future acquisitions, which would otherwise be credit positive by expanding earnings or enhancing Pfizer's pipeline".