Labour leadership rules bar hopefuls from interrupting their rivals and making opening remarks in hustings with party members, HuffPost UK understands.
The restrictive controls have been put in place by general secretary Jennie Formby as the five candidates vying to replace Jeremy Corbyn try to convince members across the country to back them.
The events, the first of which takes place in Liverpool this weekend, are arguably the most important of the leadership race as they may be the only direct contact candidates have with some members during the race.
The official guidance, seen by HuffPost UK, reads: “Candidates will not be allowed to make opening remarks and will go straight into questions. At the end of the event they will be given two minutes to make any final closing remarks.”
It also says that “no candidates will be permitted to interrupt, question or heckle their opponents” during answers to questions from the audience.
However, the party has underlined that moderators will encourage candidates to “pursue a dialogue with each other” after answers.
Opening remarks are a standard feature of debates, with the election TV debate all allowing for them.
Boris Johnson and Jeremy Hunt given time to set out their overall case to members in the Tory leadership hustings last year and previously, Labour candidates have been able to open proceedings with their own statement.
Outsiders in the contest, such as Emily Thornberry and Jess Phillips, fear the move could push them out of the debate while the frontrunner shadow business secretary Rebecca Long-Bailey will face the minimum challenge while giving their answers.
A source close to leadership candidate Jess Phillips told HuffPost UK: “Labour Party members in Liverpool want an open process and want to hear the pitches of all the candidates.
“They’ll be disappointed by the decision by the bosses in London not to have allowed each candidate to have opening remarks.”
Deputy leadership candidate Rosena Allin-Khan, added: “Labour members, affiliates and our trade union friends want to take these opportunities to hear about our visions for taking Labour forward, which is why I’m disappointed that there will be no opening remarks at hustings.
“Taking audience questions is a fanstastic way to hear directly from Labour supporters, but we must be allowed to also set out our stalls at the start.
“The leadership elections are the most important in decades - I hope the party will reconsider.”
Other tight rules include candidates having just 40 seconds to answer questions and being “prompted by the moderator chair when they have 15 seconds remaining”. The guidance adds that the chair can press candidates further on their answers.
The Labour Party said that candidates will be allowed closing remarks and the party would ensure all were treated fairly during debates.
HuffPost UK revealed last week that the party had edited the code of conduct to also stop candidates from criticising staff.
It comes as Long-Bailey won backing from Momentum, the grassroots organisation that supports Jeremy Corbyn’s leadership, after a yes/no poll of members.
Backbencher Lisa Nandy, meanwhile, has won plaudits for her performance in an interview with veteran BBC journalist Andrew Neil.
The Labour leadership debates will take place in Liverpool, Durham, Bristol, Cardiff, Birmingham, Glasgow and London.
The winner is decided on a ballot of members by a proportional representation system known as AV (alternative vote), which sees candidates ranked in order of preference.
If one of the five wins more than 50% of first preference votes, they are declared the winner outright. However, if no candidate hits 50%, the candidate with the least support is eliminated and their second preferences are allocated to the remaining contenders. That process is repeated until one candidate reaches that crucial 50% mark.
The winner is announced at a special conference on April 4.