Apple's iPhone is turning into a worldwide loss leader, according to a report from Danish market researcher href=http://www.strandconsult.dk/>Strand Consult, which said in a report released Monday that it could find no global carrier that increased profits by offering the iPhone.

The iPhone-AT&T situation is well known, whereby AT&T impacts its earnings by subsidizing iPhone sales in return for landing all-important new cell phone subscribers and potential revenue from future data plans.

After surveying global carriers offering the iPhone, Stand Consult said it couldn't find any carriers marketing the iPhone whose profits were increased.

"According to the research we have conducted on the operators, not one of these has increased their market share, revenue, or their earnings as a result of introducing the iPhone," Strand Consult said in the report. "When looking at the numbers we can't see the iPhone effect -- a lot of competitors are actually doing better."

The AT&T-iPhone situation may be illustrative of the worldwide carrier-iPhone phenomenon in which Apple has set up exclusive arrangements for marketing of the iPhone. In its last quarter, reported in July, about two-thirds of AT&T's new 1.4 million wireless subscribers signed up for an iPhone. At the time, Nielson Co. analyst Roger Entner estimated that AT&T was subsidizing the iPhone to the tune of $720 million in the quarter.

AT&T -- and other providers of the iPhone -- generally view the popular iPhone as a means of enticing cell phone users from competitors and, once in the AT&T family, as a means of bringing in escalating revenues in the future.

Strand Consult also said its research showed that the closer a carrier is to Apple, "the larger negative influence it has on the operator's overall business case from a shareholder's viewpoint."

For instance, the telecom market research firm said that iPhone launches caused falling profits at SingTel, negatively impacting operating profit margins by 3-4 percentage points. SingTel is the largest phone company in Southeast Asia.

Strand Consult's report also suggested that iPhone competitors are beginning to catch the iPhone, often with features similar to those that have been so popular on the iPhone.

InformationWeek has published an in-depth report on smartphone security. Download the report here (registration required).