WASHINGTON/NEW DELHI (Reuters) - Ten U.S. senators called on the Food and Drug Administration to reject Philip Morris International Inc's PM.N application to market its iQOS smoking device as being less risky than cigarettes, according to a letter to the agency's commissioner.

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The senators, all Democrats, cited remarks by an expert scientific panel that reviewed the application for the FDA and voted last month to recommend against granting Philip Morris permission to do so, according to the letter, a copy of which was seen by Reuters.

The senators also referred to a Reuters report in December that identified shortcomings in the training and professionalism of some of the lead investigators in the clinical trials submitted to the FDA by Philip Morris, the maker of Marlboro cigarettes. Former Philip Morris employees and contractors also described irregularities in those experiments.

Philip Morris International, the world’s largest publicly traded tobacco company by market value, has applied to the FDA to be able to sell iQOS in America and for permission to market it as a modified-risk tobacco product. That designation could mean that Philip Morris would be allowed to sell iQOS to consumers as presenting less harm or risk of disease than traditional tobacco.

By heating tobacco instead of burning it, the company says iQOS avoids subjecting smokers to the same levels of carcinogens and other toxic substances found in regular cigarettes. The device is part of a $3 billion-plus investment by Philip Morris in new-generation smoking platforms.

The senators’ letter, dated Feb. 7, asked FDA Commissioner Scott Gottlieb to “avoid rushing through new products, such as IQOS, to fit within this evolving FDA policy, without requiring strong evidence that any such product will reduce the risk of disease, result in a large number of smokers quitting, and not increase youth tobacco use.”

It also said: “Such thorough review is especially critical given the tobacco industry’s deceitful history of marketing products under the guise of lower risk.”

The signatories include Elizabeth Warren, a prominent Democratic voice in the Senate, and five members of the Senate’s powerful appropriations committee, including Dick Durbin and Jack Reed.

Durbin and Senator Richard Blumenthal, who also signed the letter, released statements to Reuters at the end of last month expressing concern about the iQOS application to the FDA.

An FDA official said on Wednesday the agency had received the letter and would respond directly to the senators.

Philip Morris did not immediately respond to requests for comment. A company spokesman referred to a Jan. 29 statement in which Chief Executive Andre Calantzopoulos said, “We look forward to working with the agency to clarify outstanding points so as to best assist in their ongoing decision-making process, which inherently entails a certain degree of scientific uncertainty pre-market.”

The advisory panel said Philip Morris had not proven that iQOS reduced harm compared with cigarettes. It did conclude that iQOS exposes users to lower levels of harmful chemicals, but said the company had not shown that lowering exposure to those chemicals is reasonably likely to translate into a measurable reduction in disease or death. The recommendation is not binding.

Since the first of two days of meetings by the FDA scientific advisory panel on Jan. 24, which expressed doubts about Philip Morris’ application to the agency, the company’s stock has fallen about 9 percent as of the market’s close on Tuesday. The stock was down 0.7 percent Wednesday afternoon.

Philip Morris is scheduled to release its fourth-quarter earnings report on Thursday.