Rachel Riley, the presenter of Countdown, has won the first round in a high court libel claim over a tweet sent by a former senior aide to Jeremy Corbyn.

Riley is suing Laura Murray over a message posted a short time after the former Labour leader was hit by eggs thrown by a Brexit supporter during a visit to Finsbury Park mosque on 3 March 2019.

Shortly after the incident, the 34-year-old TV presenter tweeted a picture of an earlier tweet by Guardian columnist Owen Jones about an attack on former British National party leader Nick Griffin, in which Jones said: “I think sound life advice is, if you don’t want eggs thrown at you, don’t be a Nazi.”

On 3 March, Riley replied, “Good advice”, with an emoji of a red rose and an egg. Later that day, Murray tweeted: “Today Jeremy Corbyn went to his local mosque for Visit My Mosque Day, and was attacked by a Brexiteer. Rachel Riley tweets that Corbyn deserves to be violently attacked because he is a Nazi. This woman is as dangerous as she is stupid. Nobody should engage with her. Ever.”

Riley has described Murray’s tweet as an “appalling distortion of the truth” and is now suing for damages. She says Murray’s tweet contained “defamatory statements of fact” about her. In her defence, Murray argued that the tweet was not defamatory and was a statement of her opinion.

On Friday, following a preliminary hearing conducted by written submissions, Mr Justice Nicklin ruled that the meaning of Murray’s tweet was that Riley “had publicly stated in a tweet that he [Mr Corbyn] deserved to be violently attacked”.

The judge also ruled that the part of Murray’s tweet which said Riley was “as dangerous as she is stupid” was an expression of opinion, which meant that Riley had “shown herself to be a dangerous and stupid person who risked inciting unlawful violence”.

Nicklin said both of those parts of Murray’s tweet are defamatory in common law. He rejected the contention, advanced by Murray’s lawyers, that a reasonable reader of her tweet would understand the reference to Riley supposedly stating that Corbyn “deserved to be violently attacked” to be an expression of opinion.

Concluding, Mr Justice Nicklin said: “An imputation that a person had publicly supported a violent attack on someone is plainly defamatory at common law. It is conduct which would substantially affect, in an adverse manner, the attitude of other people towards the claimant or have a tendency so to do.”