The party feels that the branding unfairly favours Boris Johnson, who is trying to frame the election as a vote on EU withdrawal with his main pledge to “get Brexit done”, while Jeremy Corbyn is seeking to widen the debate to issues such as health and austerity.
HuffPost UK understands Labour has exhausted complaints to Sky News and will now ask regulator Ofcom, which has already had 65 complaints about the branding, to rule on whether the broadcaster is breaching impartiality rules.
The “Brexit election” branding, which appears several times a day on Sky News, has caused unease among staff, with one insider admitting that “some of us have real worries about the Brexit framing”.
“It’s doing us no good at all,” another added.
A Labour source told HuffPost UK: “This does the Tories’ work for them, effectively ensuring their Brexit election slogan is on screen and all over social media all day, every day.
“It’s for voters to decide what’s important to them, and this election is about more than one issue and about the real change we need after a decade of cuts under the Tories and Lib Dems.”
Former culture secretary Ben Bradshaw said the branding could breach impartiality rules if it is found to “adopt the narrative” of one party over another.
Bradshaw, who is defending Exeter for Labour, told HuffPost UK: “Brexit is a huge issue at this election, however it is completely wrong for any public service regulated broadcaster to brand it as such in their branding.
“It’s not up to Sky News to decide what the subject of this election is.
“Certainly people’s concerns about the ongoing uncertainty and the economic damage of a hard or no-deal Brexit under the Tories is a huge issue in a seat like mine.
“But there are other very big issues - we are picking up a lot of concerns about the future of the health service under this Trump-Farage-Johnson axis, and a lot of concern about the government’s failure to publish the Russia report and the influence of Russian money in Tory politics.”
He went on: “I think it’s potentially problematic if the broadcaster adopts the narrative of one or the other of the political parties.
“If one of the political parties is trying to brand the election as about one thing, and a broadcaster seems to be siding with them then that is not impartial, that is against the impartiality rules under the representation of the people act.”
Steve Barclay, the Brexit Secretary, said: “This type of complaint tells you everything you need to know about Corbyn’s Labour – they have an utterly incoherent position on Brexit and now want to run away from it.
“If it wasn’t for Labour’s dither and delay we could have left the EU on October 31. Instead, their indecision gridlocked parliament.
“The choice at this election is simple. A Conservative majority government with Boris Johnson that will get Brexit done so we can move on to the people’s priorities – or Jeremy Corbyn inflicting the chaos of two referendums on the British people.”
Sky refused to comment.