The CEO of Mylan (MYL), the generic pharmaceutical company, which itself pursued an inversion with healthcare company Abbott Laboratories earlier this year, has been an outspoken defender of the controversial and increasingly popular practice in which corporations acquire a foreign company for its more favorable, foreign tax rates.

Earlier today, at Fortune’s Most Powerful Women conference in Laguna Niguel, California, she was standing by her story. “There’s lots of misperceptions,” she said of the practice, which she says is being used as political rhetoric to stir the public in an election year.

Instead, she calls tax inversion a necessary practice for an American company to remain competitive and ultimately, growing in America. She says this is particularly true in the pharmaceutical industry; in America, 50% of drugs are imported. It’s on Congress, she says, to “fix the broken tax code” and make America an attractive place to domicile a company in the global economy.

Susan Kilsby, Chairman of British drugmaker Shire, which was acquired by AbbVie (ABBV) in another of the year’s pharmaceutical inversions, noted that without American tax reform corporations that have inverted will be far more likely to pursue investment abroad. “When earnings are trapped overseas, it’s much more efficient to build a facility overseas.”

Kilsby added that shareholders in the US and UK have become more engaged with the wave of inversions.”It’s changed the way shareholders act. They’re being far more vocal with boards.” When Shire became an inversion target, she began getting nightly calls from shareholders to her home phone. Such calls, per British rules, must be “chaperoned” and Kilsby would quickly scramble to call bankers and get one on the call.

While shareholders in the US can’t ring up board members like they can in the UK, panelists noted that activist investors in the US have increasing presence and are “here to stay.”