Romelu Lukaku has been on fire for Manchester United this season

Lukaku has quickly affirmed himself as a fan favourite to the United faithful.

The Belgian star has scored eight goals in eight games for the Red Devils - a better record than previous greats Eric Cantona, Zlatan Ibrahimovic and Wayne Rooney.

However, a number of fans have took to singing a chant referencing the striker’s penis size which has caused controversy.

Both the club and player have had their say on the matter, urging supporters to refrain from singing it.

Anti-discrimination body Kick It Out have also weighed in saying the song is “offensive and discriminatory”.

But when the former Everton man scored against Southampton today early in the first half, the chant could be heard along with “we’ll sing what we want”.

And now the Manchester club have ramped up their matters to put an end to it by contacting the police.

A United spokesperson said: "Manchester United has a zero tolerance stance on offensive chanting and behaviour.

"The club and player have been clear in asking for an end to the chant.

"The club has worked with relevant bodies and supporters groups in trying to eradicate any offensive behaviour and will take further action against individuals if this continues.

"The club is in discussion with the police and has asked for CCTV footage from Southampton and will try to identify those who disrespected the player's wishes not to sing the song."

United manager Jose Mourinho was keen to avoid the matter in his post-match interview.

"I don't understand what the fans sing," he said.

"The only music I understand clearly is one from my opponents when they tell Mourinho to go to a place. That's the only one I understand.

"But the only thing I will say is the fans were amazing, the support amazing from the first to the last minute.

"It's important to have that not when you're winning 3-0 or 4-0 and winning the game, but it's more important when you are defending and are exhausted. The songs? I don't understand them."