The decisions by Pfizer to move its tax address to Ireland by buying Dublin-based Allergan, has met with strong political condemnation in the US.

Presidential hopeful Hillary Clinton says the proposed merger, and so-called inversions by other companies, will leave US taxpayers holding the bag.

Her republican rival Donald Trump also denounced the deal, saying it's disgusting that Pfizer is leaving the country with a tremendous loss of jobs.

The merged company will no longer be taxed as a US company.

Business Journalist Vincent Wall says preventing other companies doing the same requires action by Congress: