A 17-year-old boy has been arrested over a string of malicious tweets he allegedly sent to the teenage diver Tom Daley over his failure to win an Olympic medal in a case that has raised fresh questions over the policing of comments on social media.

The teenager – who tweeted by the name of @Rileyy_69 – was arrested at 2am yesterday and was being questioned by Dorset police after the young diver retweeted a comment suggesting that Daley had let down his late father who died last year from brain cancer.

The teenager was arrested under the Malicious Communications Act. It carries a maximum sentence of up to six months in prison and a fine of up to £5,000 for a communication “which conveys a message which is indecent or grossly offensive.”

[...]Daley retweeted a message which said: “You let your dad down i hope you know that." Daley responded by tweeting: "After giving it my all... you get idiots sending me this..."

Further abusive messages from the same address followed suggesting that the sportsman had “failed” and made a violent threat towards Daley and other Twitter users.

As news of his tweets spread, Rileyy_69 attempted to apologise to Daley. He later added: "please i don't want to be hated I'm just sorry you didn't win i was rooting for you pal to do britain all proud just so upset.”