PARIS — Mobile satellite services providers Inmarsat and Iridium Communications, which by most counts occupy the top two slots in market share, have extended their rivalry to include dueling consultancy reports that reach sharply different conclusions about the quality of their competing services.

In September, an Iridium-commissioned Frost & Sullivan report concluded that London-based Inmarsat, whose IsatPhone had debuted on the market only weeks before, had not been able to provide regular handset reception in Alaska. In another jab, the Frost report concluded that the Inmarsat phone took much longer than Iridium’s phone to boot up, find an available satellite and make itself ready for use.

On Feb. 4, consultancy TelAstra Inc. responded with an Inmarsat-commissioned survey that questioned almost all of Frost’s conclusions and said it is Iridium’s coverage in Alaska, not Inmarsat’s, that is difficult to secure and, once established, often falls off.

Both analyses purport to show results of users attempting to use the phones in different locales. Battery life, the phone’s ease of use and its size, and the calls’ clarity are all compared.

TelAstra President Roger Rusch, whose report is accompanied by a YouTube video showing him using the Iridium and Inmarsat gear — as well as the mobile satellite phone marketed by Thuraya of the United Arab Emirates — in various places, said he could not explain such different results.

“Our experience directly conflicts with the conclusions of the Frost &Sullivan white paper,” Rusch says in his report’s summary.

Rusch said his company had been hired by London-based Inmarsat before the Frost report came out, and that Rusch was about to begin his own tests in Alaska when the Frost results were published.

The Iridium-Inmarsat face-off, which promises to intensify in the coming years as each tries to establish a presence in markets long inhabited by the other, in the past week has spilled over to Wall Street. A Morgan Stanley research note on Jan. 31 suggested that Inmarsat has taken a 30 percent share of the market for satellite phones in the six months since its introduction.

One industry official who tracks both companies’ phones and has no reason to favor one over the other said it would be surprising if Inmarsat had eaten into Iridium’s market-leading position in handsets that quickly.

McLean, Va.-based Iridium officials say they are tracking Inmarsat’s progress in the market but that so far they have not noticed any serious challenge to Iridium’s 9555 handset despite the IsatPhone’s lower cost. They say that many sales agents will offer the Iridium product first because retailers make more money selling the 9555 than the Inmarsat product.

A Raymond James research note on Feb. 1 also doubted that Inmarsat had established such a large presence in the hand-held market.

The Raymond James note seized on the Frost report to cast Inmarsat’s “heavily promoted and deeply subsidized IsatPhone [as] a markedly inferior product, as evidenced by a recent Frost & Sullivan report,” the research note said. “A pig with lipstick … is still a pig.”

Inmarsat officials have said they will refrain from giving specific numbers of IsatPhone’s manufactured, distributed and under user contract until the product has had more time to prove itself. Inmarsat said it believes the satellite telephone market is headed for slow growth in the coming years and that it is seeking a 10 percent market share.

Peter B. de Selding was the Paris bureau chief for SpaceNews.