Television presenter Rachel Riley has told a High Court judge that she thinks an aide to then-Labour leader Jeremy Corbyn who described her as “dangerous” and “stupid” in a tweet two years ago was blowing a “dog whistle”.

Ms Riley, 35, a numbers expert on Channel 4 game show Countdown, told Mr Justice Nicklin how she believed Laura Murray was aware that the March 2019 tweet would “encourage more hate”.

She has sued Ms Murray for libel, wants damages, and says the tweet caused “serious harm” to her reputation.

Ms Murray, who no longer works as an aide to Mr Corbyn, says in her defence that what she tweeted was true, and reflected her honestly held opinions.

Mr Justice Nicklin is overseeing a trial at the High Court in London, which began on Monday and is due to end on Wednesday.

Ms Riley, who studied mathematics at Oxford University, has told the judge that she is Jewish and has a “hatred of anti-Semitism”.

She said she spoke out against anti-Semitism and thought the Corbyn-led Labour Party was “fostering anti-Semitism”.

Ms Murray posted her tweet on March 3 2019 after an egg was thrown at Mr Corbyn by a Brexit supporter when he was visiting Finsbury Park Mosque in north London.

She was responding to a tweet posted by Ms Riley, the judge has heard.

Ms Riley had initially posted a screenshot of a January 2019 tweet by Guardian columnist Owen Jones, about an attack on former British National Party leader Nick Griffin, which said: “I think sound life advice is, if you don’t want eggs thrown at you, don’t be a Nazi.”

She had added “Good advice”, with emojis of a red rose and an egg.

Later, Ms 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.”

Ms Riley told the trial on Tuesday that she had been criticised by other Twitter users after posting the good advice tweet before Ms Murray joined the discussion.

“I believe it was dog whistle,” Ms Riley told the judge.

“There were however many people attacking me and telling me I was terrible and awful.

“Three hours later Laura Murray decides to take it to an extra layer.”

Ms Riley added: “I believe she was aware of what she was doing.

“She was aware that she would encourage more hate.”

Mr Justice Nicklin had ruled at an earlier hearing that Ms Murray’s tweet was defamatory.

The judge concluded that the tweet meant that: Ms Riley had “publicly stated” Mr Corbyn had been attacked when visiting a mosque; that he “deserved to be violently attacked”; by doing so, she had shown herself to be a “dangerous and stupid person” who “risked inciting unlawful violence”; and that people should not “engage with her”.

He has now been asked to consider whether serious harm was caused to Ms Riley’s reputation, and whether Ms Murray had a defence of truth, honest opinion or public interest.

Ms Riley has said she was being sarcastic in her tweet and had not called Mr Corbyn a Nazi.