According to The Guardian, a senior party figure close to the talks revealed that the laboured process is draining any spontaneity from the initiative.
Last week, representatives from the Conservatives, Labour and Liberal Democrats held discussions with the BBC, Sky and ITV about the debate formats. However, important issues such as the level of audience participation remained undecided.
All three broadcasters have agreed to host a 90-minute debate programme at peak time in the run-up to the general election in May.
David Dimbleby, who will host the BBC's edition, recently claimed that the debates will be a "turning point" for British democracy.
The Liberal Democrats reportedly want the format to be similar to BBC One's Question Time, in which questions arise from the studio audience, as well as the programme host.
However, no decision has been made on how the audience will be selected, particularly whether it should be made up of supporters of each party or simply a broad stroke of the population.
Party leaders are well aware that the audience reaction would play an important role in influencing the perception of people watching at home, with a high probability of reputational damage should they get a poor reaction in the studio.
All three broadcasters want the debates to carry a theme, but the parties are still deadlocked on the length of opening statements and whether the leaders should be able to interrupt each other to argue their points.
In the US, televised presidential debates carry detailed guidelines on everything from podium size to the ability of participants to only ask rhetorical questions of rivals.
A coin toss is made between the candidates 72 hours before transmission to decide who asks the first question and delivers the final statement.