Democratic US presidential candidates Hilary Clinton and Bernie Sanders have responded angrily to the latest so-called inversion merger of US companies driven by the expected $150m per year tax advantages arising from relocating their combined HQ in Ireland.

Milwaukee-based Johnson Controls, a manufacturer of car batteries and heating and ventilation equipment is to acquire Cork-based fire-controls company Tyco in a $16.5bn deal. Tyco moved its affairs to Ireland from Switzerland less than two years ago.

Shareholders in Johnson are to be offered $4bn in cash to reduce their holding in the combined company allowing Tyco to own more than the 40% threshold required for inversions to take place under current regulations.

"These efforts to shirk U.S. tax obligations leave American taxpayers holding the bag while corporations juice more revenues and profits," Ms Clinton said in a statement which called the deal "outrageous."

"I have a detailed and targeted plan to immediately put a stop to inversions and to block deals like Johnson and Tyco and place an exit tax on corporations that leave the country to lower their tax bill," she continued.

Bernie Sanders has called it a disaster for American taxpayers. "Profitable companies that have received corporate welfare from American taxpayers should not be allowed to renounce their U.S. citizenship to avoid paying U.S. taxes," he said.

The reaction echoes the response to the much larger proposed inversion merger of Allergan and Pfizer announced late last year.

Republican frontrunner Donald Trump says that poor tax regulations in the US are to blame for these countries leaving the country. He wants to slash the US corporate tax rates by more than half.