BBC News presenter Martine Croxall is understood to have been taken off air following a potential breach of impartiality during Sunday night's edition of The Papers.
During her introduction to the programme, which started at 10.30pm on Sunday around 90 minutes after Boris Johnson pulled out of the Tory leadership race, Croxall said: "Well this is all very exciting isn't it?"
"Am I allowed to be this gleeful? Well I am," she told viewers.
In her first question to her guests she also remarked: "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 Because all the front pages were probably out of date by the time we received them."
Some viewers, including several Tory MPs reacting to a clip on social media, complained it displayed bias.
A statement from the broadcaster 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."
It is now understood that Croxall has been taken off air following the review, according to PA news agency.
Following Martine's comments on The Papers, many viewers took to social media to share their frustration – with some calling for an Ofcom investigation.
"Martine Croxall of BBC News shows her bias when surely a newsreader should be impartial. Unfit for the job," said one angry viewer.
While a second added: "@Ofcom please moderate horribly biased @BBCNews woman Martine Croxall @MartineBBC shouting over @ScottBentonMP for daring to support the democratically elected @BorisJohnson It's unrepresentative and intolerable that have to pay her wages or go to jail."
A third tweeted: "Martine Croxall is rightly being pilloried for this partisan display of giddy excitement as News broke of Boris Johnson dropping out of the Leadership contest. This lapse of impartiality and professionalism illustrates why so many accuse the BBC of bias."
The BBC has a strict set of guidelines for employees which prohibits them from expressing any bias, with Section 4.1 of their editorial guidelines stating: "The term 'due' means that the impartiality must be adequate and appropriate to the output, taking account of the subject and nature of the content, the likely audience expectation and any signposting that may influence that expectation."
The Mirror has approached the BBC for further comment.
