Boris Becker has said an Alternative for Germany (AfD) MP accused of posting a “clearly racist” tweet about his son must now face “consequences”.
The German tennis champion said that an attempt by Jens Maier to distance himself from the post was a “trick”.
It comes after a tweet posted on the far-right politician’s account referred to Noah Becker as “little half-negro”.
Noah Becker has an African-American grandfather on his mother’s side. Mr Maier denies writing the tweet.
The post has since been deleted from the Twitter account linked to Mr Maier, who has blamed one of his staff members.
In a column written for the German newspaper Welt am Sonntag, Mr Becker said the denial by Mr Maier was a common response from members of Germany’s AfD party.
“That’s what the AfD always does; it’s their trick: put something out there in the world and then distance yourself from it,” he wrote.
He also praised his 23-year-old son Noah, who has filed a criminal complaint over the incident, for his ability to “fight hatred with love”.
In an interview with Vice magazine on Friday, Noah said that some people simply needed to be more “open”.
“[Noah] said that those who don’t know the world, who haven’t seen people with different skin colours or people who think differently, become scared,” Mr Becker wrote.
“I have to admit he’s one step ahead of me – I want there to be consequences first,” the three-time Wimbledon champion added.
The tweet posted on Mr Maier’s account was written in response to an interview Noah Becker gave in which he described Berlin as “a white city” compared to other European capitals, and said he had been attacked there because of his skin colour.
“It seems the little half-negro simply got too little attention – that’s the only explanation for his behaviour,” the message posted to Mr Maier’s account on Tuesday said, in German.
Mr Maier is the parliamentary deputy for the AfD party, which received almost 13% of the vote and won over 90 seats in last year’s election.
“I have been retained to quickly take the necessary steps under criminal and civil law against MP Jens Maier on the basis of this clearly racist tweet,” Becker family lawyer Christian-Oliver Moser told Bild, a German newspaper.
The head of Germany’s federal judges association, Jens Gnisa, condemned the tweet as completely unacceptable.
Mr Moser confirmed to Germany’s DPA news agency that a criminal complaint had been filed on Wednesday.
Two other members of the far-right political party are being investigated over anti-Muslim messages they posted on New Year’s Eve.
On 1 January, a law requiring social media companies to act quickly against hate speech came into force in Germany. Platforms that don’t may face fines of up to 50m euros (£44.3m).