US car battery and building efficiency specialist, Johnson Controls has agreed to merge with Cork-based fire prevention and security products company Tyco International and move its headquarters to Ireland in a tax-saving ‘inversion’ deal.

Wall Street’s fortunes turned negative again today as a downgrade of chip makers by Merrill Lynch and retailers’ disappointing sales gave investors more reasons to doubt the strength of a business recovery. Stocks fell sharply, with the tech sector suffering the heaviest losses.

Bargain hunting lifted US tech stocks moderately higher today, but the overall market fell on news that yet another company, Knight Trading, was being investigated by the government.