The Electoral Reform Society says the £75million ballot could end with a turnout of just 18.5 per cent - the lowest in history for a nationwide poll and way below the 65 per cent recorded at the last general election.
It accuses the Home Office of "shirking its responsibility" by refusing to post general information to voters, holding the election by itself in November rather than with other ballots, failing to run a helpline until just a few weeks before polling day, and only providing information online where it is inaccessible to millions of elderly and disadvantaged people, the blind and those who cannot read English.
The group, which campaigns for better democracy, adds that independent candidates will be particularly hampered by the lack of publicly-funded information about the PCC elections as they will not have the same funding and supporters as those backed by the major political parties.
It warns that low turnout could help extremist candidates, who would be unable to win the backing of the majority, and jeopardise the legitimacy of those who go on to hold the powerful new post.
PCCs, who will be paid up to £100,000 a year for a four-year term, will set police force budgets and strategies in 41 areas across England and Wales and will be able to hire and fire chief constables.
Low turnout would undermine the purpose of creating the US-style sheriffs, as ministers hoped they would make police chiefs more accountable and reconnect them to residents.
Katie Ghose, chief executive of the Electoral Reform Society, said: "This election is beginning to look like a perfect storm, which could result in the lowest turnout for a national election in British history.
"Those pulling the strings have not done their homework and as a result this election looks primed to degenerate into a complete shambles.
"Put simply, if the people elected to localise decision-making over how our streets are policed, do not represent local people, what is the point of having them?"
Meanwhile preparations for the elections on November 15, already thrown into disarray by a row over which criminal convictions count as a bar to potential candidates, have suffered another blow as a senior judge completed an about-turn on the role of magistrates.
Lord Justice Goldring, the Senior Presiding Judge, had decreed that JPs could neither stand as PCCs nor sit on new oversight panels because of the risk it would damage the independence of the judiciary.
But after campaigners pointed out that magistrates currently sit on police authorities and can also serve as councillors and MPs, and had not been barred when Parliament drew up the law, he was forced into a climbdown.
On Friday the judge issued new guidance merely stating that magistrates must "ask themselves" whether or not they can hold office both as a PCC and a JP.
He also backed down on his earlier ban on magistrates serving on Police and Crime Panels.
Mervyn Barrett, an independent candidate in Lincolnshire who organised a meeting with the judge, said afterwards he was "delighted" by the outcome.
Simon Duckworth of the Association of Police and Crime Commissioners' Transitional Board, added: "Magistrates' wealth of insight and experience make them perfectly placed to help monitor those who will 'police the police'."
The think-tank Policy Exchange, which has long campaigned for PCCs in Britain, has created the most detailed website about candidates and told ministers they should be on television selling the policy.
But Nick Herbert, the Police Minister, has insisted the "carping" about the elections is just a "silly season" story.
A Home Office spokesman said: "Police and Crime Commissioners will, unlike invisible and unelected police authorities, give local communities a say over policing priorities in their areas and work with the police to cut crime."
