"In emerging markets, the iPhone 4S will continue to be the volume driver at the low end as the lack of subsidy in most markets leaves the iPhone 5c too highly priced to help drive further penetration," Gartner said.
Apple did not immediately reply to an email seeking comment on the issue.
In India, Apple is selling 16 GB iPhone 5c at Rs. 41,900 and 32 GB variant at Rs. 53,500, while, iPhone 5s is available at Rs. 53,500 (16GB), Rs. 63,500 (32 GB) and Rs. 71,500 (64 GB).
"Gartner believes the price difference between the iPhone 5c and 5s is not enough in mature markets, where prices are skewed by operator subsidies, to drive users away from the top of the line model," it added.
A contract-free and unlocked 16GB version of the iPhone 5c is available for USD 549 (about Rs. 34,700) in the US, while an unlocked and contract-free iPhone 5s can be bought for USD 649 (about Rs. 41,000).
In the July-September quarter of 2013, Apple's smartphone sales reached 30.3 million units, up 23.2 percent from the same quarter of 2012.
"While, the arrival of the new iPhones 5s and 5c had a positive impact on overall sales, such impact could have been greater had they not started shipping late in the quarter," Gartner said.
The firm added that there has been some inventory built up for the iPhone 5c, whereas the demand for 5s has been good leading to its stocks being sold out in many markets.
Besides, the research firm said that worldwide sales of mobile phones are expected to rise by 3.4 percent to touch 1.81 billion units this year compared to the previous year.
The firm, while giving July-September 2013 mobile phone sales data, said globally mobile phone sales touched 455.6 million units in the third quarter, clocking a growth of 5.7 percent from the same period last year with smartphones sales accounting for a record 55 percent of the overall sales.
Worldwide smartphone sales reached 250.2 million units, up 45.8 percent from the same quarter of 2012, it said.
"Asia/Pacific led the growth in both markets the smartphone segment with 77.3 percent increase and the mobile phone segment with 11.9 percent growth," Gartner added.
The regions to show an increase in the overall mobile phone market were Western Europe, which returned to growth for the first time this year, and the Americas, it said.