Jeremy Corbyn has been warned not to put too much weight on online polls to support policy changes after the Labour leader signalled he would make increased use of internet surveys of party supporters.
Former frontbencher Dan Jarvis, an ex-soldier who has been tipped as a future leader, warned that online surveys - such as the one carried out before the decision on bombing Islamic State in Syria - "short-circuit" the normal decision-making processes and could "lead to badly designed policy".
Mr Jarvis, who urged Labour to publish its inquiry into the 2015 election defeat, said the party had to understand it had been "out of step with the electorate" and win back voters' trust on the public finances.
Mr Corbyn, who was swept to victory in the Labour leadership contest on a tide of support from grassroots and internet activists, told the party in December that it had "better get used to" more social media campaigns and surveys.
Writing in the New Statesman, Mr Jarvis acknowledged that since Mr Corbyn was elected Labour had attracted tens of thousands of new members.
Labour could be a "radical force of national renewal" but there had to be changes to the way the party is organised that went beyond "the odd online poll".
"The internet plays an important role helping people who are busy juggling kids and work to engage with the party. Social media attracted many of our new members into the party and will be essential for keeping them engaged," he said.
"But we need to make sure that our members can contribute fully, beyond the odd online poll.
"These short-circuit institutional checks and balances on those in power, they lead to poorly designed policy, and if they are conducted online, they exclude those without access to the internet.
"The party needs to build leadership and organising skills among our members to harness their talent and develop a more democratic party. The value of our members should not be counted by how many million conversations we have with voters.
"We need conversations that build enduring relationships with the public, not transactional cold-calling."
Barnsley Central MP Mr Jarvis called for the publication of Labour's internal review of its election defeat so the party could see where it had failed.
"Until Labour accepts the lessons of two successive election defeats ... we will not renew our politics and reconnect with the public," he said.
"During the election I campaigned up and down the country. People frequently told me that although they knew the Tories were unfair and represented the interests of the better-off, they did not trust Labour with their taxes. We have to win back their trust.
"That's why we need to publish our official party inquiry into why we lost. Once we understand that we have been out of step with the electorate, we can start to build our political recovery and respond to the policy challenges Britain faces."
Former shadow education secretary Tristram Hunt denounced the "divisiveness and futility" of Mr Corbyn's reshuffle.
Writing in The Spectator, Mr Hunt - who refused to serve on the Corbyn frontbench - said that the shake-up had distracted attention from Labour campaigns on flooding, Europe and housing.
"You will recall that Europe spokesman Pat McFadden was sacked for suggesting that terrorists should be held accountable for their crimes. Shadow defence secretary Maria Eagle was moved for supporting Labour Party policy. And culture minister Michael Dugher got the axe for not living in Islington," said Mr Hunt.
"Kremlinologists suggest there is a power struggle going on in Jeremy Corbyn's office between the Socialist Action Mensheviks and the Bolsheviks of the Labour Representation Committee. But all factions are united in their determination to make it to 2017, and the centenary of the Great October Socialist Revolution."
A survey of more than 100 constituency Labour parties by The Guardian found that almost every one reported membership numbers at least doubling since Mr Corbyn stood for the leadership - with some saying they had five times as many members as before and others reporting the revival of branches which had been near to closing for lack of support.
Overall Labour membership has increased from 201,293 at the time of the May 2015 general election to 388,407 this month, with the total of 13,860 who have left since the election vastly outnumbered by new recruits, said the newspaper.
The Guardian reported that there had been two surges of new members signing up, the first coming after Mr Corbyn joined the battle to succeed Ed Miliband and the second after he was elected leader.
A Labour spokeswoman said that membership stood at around 380,000 in December and was continuing to grow, but declined to give further details.
In the latest stage of the reshuffle, Jo Stevens was appointed shadow solicitor general.
She takes over from Karl Turner, who was promoted to shadow attorney general on Monday following the resignation of Catherine McKinnell.