By the end of 2012, more instant messages were sent via chat apps per day than SMS text messages, according to research carried out for the Financial Times by analyst firm Informa.

Over-The-Top (OTT) messaging apps are also expected to generate 41 billion messages per day in 2013, more than double the number of text messages expected to be sent.

Operators have relied on revenue generated by SMS text messages for many years, but the rise of OTT chat apps, such as WhatsApp, Viber and Apple iMessage, has eroded this revenue source.

According to Informa senior analyst Pamela Clark-Dickson, internet-based messaging is increasingly being used as a substitute for SMS in some markets and is having “a significant impact” on operator traffic and revenue in Spain, the Netherlands and South Korea.

Informa expects text messages to generate more than $120 billion this year, showing the scale of impact chat apps could have. Text message revenue in Spain, for example, fell from €1.1 billion in 2007 to €758.5 million in 2011.

Many of these apps, which send data via mobile broadband or WiFi, also offer voice and video chat, providing further competition for operators.

In response to the findings, EU Digital Agenda commissioner Neelie Kroes tweeted: “It’s official: chat apps have overtaken SMS globally. The cash cow is dying. Time for telcos to wake up & smell the data coffee.”

Some mobile companies have fought back with apps of their own, such as Libon offered by France Telecom-Orange and Telefonica’s TuMe.

However, the cause of the chat apps is being helped by the likes of Nokia, which last week launched the low-cost Asha 210 phone featuring a dedicated WhatsApp button.