The research firm said that Sky remains the leading TV platform with an estimated 10.3 million customers in the UK at the end of the first quarter.
IHS said that Sky gained a net 400,000 subscribers year-on-year, thanks to its standalone over-the-top service, Now TV.
Without this, it said Sky experienced four successive quarters of declines for its core pay TV service – including a 52,000 satellite subscriber loss quarter-over-quarter in Q1.
Now TV had an estimated 729,000 subscribers at Q1 2015, making it the fastest-growing pay TV platform, according to the research.
TalkTalk had 1.4 million subscribers at Q1 2015, a net year-on-year gain of 54%. BT reported 1.1 million TV subscribers, excluding BT Sport customers, which was up 14%. Meanwhile, Virgin Media had 3.7 million pay TV customers, almost unchanged from Q1 2014.
In total, IHS said that there were 16.6 million households subscribing to pay TV by March 31, 2015, up from 15.6 million a year earlier.