Tottenham were on Monday investigating an alleged incident of racism by one of their supporters towards Heung-min Son in the 1-0 defeat by Manchester United.

The club is working with a season-ticket holder who tweeted during the game, writing: “I’ve not experienced racism at football for about 15 years. But today @SpursOfficial was hideous. Reported to stewards, did nothing. Confronted him myself and was called a c***. While I was standing next to my son. Disgusting.”

The supporter confirmed South Korea forward Son was the target of the alleged abuse and added: “Spurs have been in touch and I’ll work with them to find the person. Spurs...have been great.”

Last month, Spurs boss Mauricio Pochettino said he wanted to “kill racism” after a fan threw a banana onto the pitch in the 4-2 defeat at Arsenal.

Three Chelsea supporters were investigated for racially aggravated public order offences during last Tuesday’s 1-0 defeat in the Carabao Cup semi-final by Spurs and both clubs are on alert ahead of the second leg a week on Thursday.