The update will affect 3G performance of iPhone 4S devices.
Vodafone warned all UK iPhone 4S users not to update their devices to iOS 6.1, until Apple delivers a fix for the connectivity problem.
The carrier sent text messages to iPhone 4S handsets on the network saying that the update will affect their 3G performance.
Vodafone said in a statement that some customers may occasionally experience difficulty in connecting to the network when making or receiving calls and texts, as well as connecting to the internet.
"Apple is working on a solution to their software issue. These connection problems are intermittent," the company said.
"While Apple's investigations continue, we would recommend that anyone who has not yet installed iOS 6.1 on their iPhone 4s should delay doing so until Apple has confirmed that their problem has been fixed."
The warnings surface after numerous complaints from iPhone 4S users after they updated to iOS 6.1.
According to the Guardian, Three's network in Austria also warned its customers that updating to iOS 6.1 on the iPhone 4S can cause connectivity problems.
"We responded quickly and are working with Apple on a solution to the problem, the statement said.
"For this reason, we recommend not to install the update for the time being. We will inform you immediately if there is a solution."