A Bollywood record label that is predicted to become the world's most popular YouTube channel is facing a fight from devoted fans of the reigning holder.

PewDiePie, whose real name is Felix Kjellberg, is rallying his legions of followers to keep him as the platform's most-subscribed channel – an honour he has held since 2013.

With 68 million subscribers, PewDiePie holds a slim margin over T-Series, the Indian record label that was expected to dethrone him.

Data from analytics firm Tubular Labs suggested the takeover would take place on Monday, 29 October. But in the days since the prediction was made, PewDiePie has seen a surge of new subscribers.

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T-Series' popularity has proven controversial among some YouTubers, given that it is a major corporate brand that will replace PewDiePie. One supporter in particular has been leading the fight for PewDiePie, with a campaign designed to keep him as the top channel.

"I bought a bunch of billboards, went on TV, did radio ads, bought bathroom ads and much more to try and stop T-Series from passing PewDiePie in subscribers," a YouTuber by the name of MrBeast said in a video describing his efforts.

"T-Series is growing four-times faster than PewDiePie and if I don't do anything PewDiePie won't be the number one most-subscribed-to YouTuber in the world. Therefore, I spent all my money on ads so he can remain as the number one most-subscribed-to channel in the world."

One billboard bought for the campaign states: "Calling all bros! You can save YouTube. Subscribe to PewDiePie. Unsubscribe to T-Series."

A billboard used in MrBeast's PewDiePie campaign (MrBeast/ YouTube)

PewDiePie himself claims to not care if he is overtaken by T-Series, however he asked his Twitter followers on Sunday: "Are you doing your part?"

In an earlier video addressing the growth of the T-Series channel, PewDiePie said the takeover would represent a perceived shift in YouTube's support of independent creators in recent years.

"It's already a heated subject now that a company is taking over. Everyone is going on the rant, 'YouTube is not really becoming YouTube' and, 'it's never going to be the same now'," he said.

PewDiePie answered questions about T-Series on his YouTube channel this week (PewDiePie/ Screenshot)

"I don't really care about T-Series, I genuinely don't, but I think if YouTube does shift in a way where it does feel more corporate, [then] something else will take its place. I think people enjoy this connection so much, I think something else will just show up, if it feels too corporate."