A coalition of powerful American business lobbies has urged Taoiseach Enda Kenny to scrap plans for plain tobacco packaging, but the Government insists its policy on the matter is settled.

A letter to Mr Kenny by six lobbies, which represent dozens of major corporations, came days before he visited the US for St Patrick’s Day.

The groups who signed the letter include the Washington-based US Chamber of Commerce, where Mr Kenny made a speech on his trip. “I can confirm the authenticity of the letter,” said Sally-Shannon Birkel of the chamber.

Co-signatories of the letter, dated March 10th, were: the Emergency Committee for American Trade; the National Association of Manufacturers; the National Foreign Trade Council; the Transatlantic Business Council and the United States Council for International Business.

“We urge you to consider the broader implications and avoid precipitous action that could convey an unintended and adverse message to Irish companies and foreign investors,” they said.

However, a Government spokesman said the policy was agreed. “A decision has been made on plain packaging and the scheme of the Bill has been cleared.”

Minister for Health James Reilly received a mandate from Cabinet to prepare legislation five months ago. Following interventions by American politicians, the lobbies' letter marks an escalation of US resistance to the measure.

The then governor of Virginia, Bob McDonnell, wrote to Mr Kenny in December. Four senior congressmen also wrote to Ireland's Ambassador to the US, Anne Anderson, urging a reversal of the plan.

In their letter, the business lobbies wished Mr Kenny well and cited the "profound importance of business ties" between Ireland and the US.

Referring to talks on a EU-US free-trade deal, they said the protection of intellectual property (IP) rights ranked among their chief objectives.

“This is the key reason we are so concerned about the plain-packaging legislation that Ireland is currently considering,” they said. “We believe it is entirely feasible to protect the public interest without undermining effective protections for intellectual property rights. Measures comparable to those under consideration in Dublin are presently being challenged in Geneva as being inconsistent with international trade obligations, as they threaten to erode global respect for robust IP protection.”

The lobbies enjoy huge corporate support. Figures from drug group Pfizer, oil giant Exxon Mobil, tool company Stanley Black & Decker and the US unit of Toyota motors are on the executive committee of the National Association of Manufacturers.

The executive committee of the US Council for International Business includes figures from tech groups Microsoft and Oracle, conglomerate General Electric, telco AT&T, Procter & Gamble, Coca Cola, Nestlé and accountants Deloitte. Citigroup, Bank of New York Mellon, Wells Fargo and JP Morgan Chase are also on the board.

The groups said a trade deal would provide an unprecedented opportunity to create the right conditions for increased trade and investment flows, from which Ireland would be a major beneficiary.