Xi set up a task force led by Zhang Dejiang, the parliamentary chief who is about to retire, to spearhead the campaign. Zhang was assisted by two of Xi’s most trusted allies, Li Zhanshu and Wang Huning. Both were elevated to the power apex, the Politburo Standing Committee, weeks later.

Wang also revealed that shortly after the party congress, when it was announced that Xi’s political theory, “Xi Jinping Thought”, would be written into the constitution, Beijing started an internal consultation process to forge consensus and rally support. They collected more than 2,600 opinions from regional cadres and other non-communist political parties, he said.

While he did not say at what stage the idea of scrapping the term limit was first raised, the speed at which the proposal was finalised suggested it had been in the pipeline from the beginning.

The constitution was last changed in 2004, when Jiang Zemin’s “Three Represents” theory was added. That took an entire year of consultations and preparation, yet this year’s proposed revisions – which are far more dramatic – took just five months to finalise.

After the congress, the leadership held another round of discussion and decided to consult party elders in mid-December.

“The party central [leadership] has solicited opinions from a select number of old comrades within the party,” according to the report, which did not name the party elders.

Wang claimed all the people involved in this process “showed unanimous support” for the amendments, including removing the last barrier for Xi to rule the country well beyond the end of his original term limit of 2022.

While it is impossible to verify Wang’s account, observers said the narrative still provided valuable information on how this momentous decision was made.

But they said the report failed to provide any evidence to support claims the decision was unanimous, or to answer important questions such as why the proposed changes were apparently pushed ahead in haste compared to previous revisions.

A mainland-based academic, who did not wish to be named, said Wang’s report appeared to be an official response from Beijing to intense rumours and speculation about possible opposition within the leadership.

“The move is highly controversial, and we’ve seen over the past weeks the unprecedented criticism and backlash from intellectuals and businesspeople, as well as veteran China watchers around the world,” he said. “It may also have grave implications for global confidence in the Chinese leadership.”

Like many China watchers, Alexander Gabuev, a senior fellow at the Carnegie Moscow Centre, said he refused to buy into the assertion that a lot of opinion had been sought or that the proposed document had won widespread support.

“I think that’s been to me a very secretive, top-down process ... there’s a pretty wide network of people, whom as we know don’t necessarily like the idea, or at least that’s what we hear in some of the private discussions. The whole censorship of this on social media, on the internet, is an indication of that,” he said.

The mainland-based academic and other analysts believed Jiang, Hu Jintao and other party elders such as former premiers Wen Jiabao and Zhu Rongji, may have been consulted.

Although retired leaders may not like the idea – which effectively puts a stop to late paramount leader Deng Xiaoping’s effort to end one-man rule following the catastrophic Cultural Revolution – the academic said “it’s really difficult for me to imagine that any one of the party elders would go out and say that’s actually a great idea”.

Pan Chengxin, professor of Chinese foreign policy and politics at Deakin University in Australia, said that although there could have been significant disagreement among party members, they may not have openly voiced dissent, which would be tantamount to splitting the party or defying Xi’s leadership.

“Given the public nature of the announcement ... before the Two Sessions, it will be unlikely that it will be knocked back by the National People’s Congress – that would be a huge loss of face for the top leadership,” he said.

“This seems to be a rollback to the earlier days, which we know were responsible for some of the terrible mistakes the party has made, such as the Cultural Revolution and the cult of personality during the Mao period, so you would think that they would be very careful not to be seen as going backwards,” he said. “But for many people this [amendment] is certainly not in the right direction.”

Highlighting the sensitivity of the proposed amendments, which include enshrining Xi’s political ideology into the constitution and setting up a super anti-graft agency, Beijing has said that the voting process on the revisions on Sunday will not be open to the media.

Additional reporting by Sarah Zheng