A BBC News presenter has been taken off air over a “potential breach of impartiality” after Boris Johnson pulled out of the Conservative leadership race. Martine Croxall said she was “gleeful” during her introduction to Sunday evening’s edition of The Papers, in which experts discuss the main news stories of the day. The programme began at 10.30pm, about 90 minutes after Johnson announced he would not stand in the contest. Croxall said: “Well this is all very exciting, isn’t it?” adding: “Am I allowed to be this gleeful? Well I am.” The comment attracted criticism on social media, including from Tory MPs such as the former culture secretary Nadine Dorries, who said it showed bias. Dorries, who had backed Johnson’s failed bid to return as prime minister, tweeted: “This lack of impartiality demonstrates how deep seated the bias is.” Croxall asked one of the programme’s guests: “Can we even show you the front pages just yet, have they arrived? No, they haven’t arrived. “It’s all a little bit, you know, lastminute.com isn’t it? Because all the front pages were probably out of date by the time we received them.” The host acknowledged she may have breached the public broadcaster’s guidelines when she laughed at guest’s comment mocking the former prime minister. “I shouldn’t probably [laugh],” she said. “I’m probably breaking some terrible due impartiality rule by giggling.” In a statement on Monday, a spokesperson for the BBC said: “BBC News is urgently reviewing last night’s edition of The Papers on the news channel for a potential breach of impartiality. “It is imperative that we maintain the highest editorial standards. We have processes in place to uphold our standards, and these processes have been activated.” The PA news agency reported that Croxall would remain off air until the investigation was complete. It came as Johnson announced he would not stand in the Conservative leadership race, prompting speculation that he had not managed to secure the required number of 100 MPs to support his nomination. He never formally declared but he had told supporters he wanted to run, drumming up backing from seven cabinet ministers. Last week, the Channel 4 news anchor Krishnan Guru-Murthy was taken off air for a week after he was caught making an offensive comment off-camera about the Northern Ireland minister Steve Baker. During an off-air moment after his exchange with Baker last Wednesday, Guru-Murthy was heard to say: “What a cunt.”