Cristiano Ronaldo fans are brutally trolling Wayne Rooney on Instagram post for his son

Cristiano Ronaldo fans have left several unpleasant comments on Wayne Rooney's Instagram post about his son, Kai.

The Manchester United forward pulled no punches while discussing his former teammate in a box-office interview with Piers Morgan.

Ronaldo was quizzed about money and fame by Morgan, with the TalkTV host asking the five-time Ballon d'Or winner if he has more money in the bank or more Instagram followers.

Through a chuckle, the 37-year-old said: "That’s a good question! Probably similar!"

Morgan replied: "I’m just trying to work out how Wayne Rooney could hate you even more!"

Ronaldo immediately retorted: "Not only him, imagine the rest of the rats they are going to criticise me too, but it is good to still be the number one."

Earlier in the conversation, Ronaldo hinted at Rooney being 'jealous' of his success and longevity in the game.

The Portugal international's die-hard fanbase has used this as an opportunity to mock Rooney on social media.

One of Rooney's most recent posts is a birthday message for his son, Kai, who turned 13 earlier this month.

He captioned a post of himself, Kai and his second-oldest son Klay: "Happy 13th Birthday @kairooney.10. Teenager."

It didn't stop the comments becoming an absolute mess, with supporters of Ronaldo believing Rooney has 'disrespected' him with comments made earlier this year.

Someone said: "Have you ever won the Ballon d'Or? Cristiano has done more than you."

A second commented: "Stop talking about CR7. Who even are you?"

While another put: "Never talk about my man Ronaldo again."

Rooney played with Ronaldo for five years between 2004 and 2009. The duo won three Premier League titles and the Champions League together before Ronaldo joined Real Madrid.

The 37-year-old is United and England's all-time top goalscorer and regarded as one of the greatest players of his generation. In defence of Rooney, someone wrote: "How f**king disrespectful are these comments? Have some respect for the greatest Englishman to grace the game, please. He said nothing wrong about Ronaldo, just a bit of constructive criticism."

It's expected Ronaldo will leave United in the January transfer window after putting manager Erik ten Hag to rights during the chat with Morgan.