A study by the left-leaning Jimmy Reid Foundation found that those making and influencing policy decisions are overwhelmingly higher-rate taxpayers and other top earners, while those struggling on lower incomes are virtually excluded from the system.
The imbalance is an invitation to "group think", the report warned, under which a small, well-off elite shapes policy to fit its own preferences and prejudices rather than basing it on facts.
There is a risk the daily concerns of most Scots are overlooked, and that people feel increasingly disconnected from politics.
To help open up the decision-making process to a wider diversity of people, the Jimmy Reid Foundation will tomorrow launch a Commission on Fair Access to Political Influence chaired by Larry Flanagan, general secretary of the EIS teachers' union, and funded by the Joseph Rowntree Reform Trust. The Trust also funded the Foundation's current report.
The commission members also include Will Dinan, the academic behind the Spinwatch website which monitors lobbying and PR; Willie Sullivan, of the Electoral Reform Society Scotland; and the SNP-turned-Independent MSP Jean Urquhart.
The Jimmy Reid Foundation's report, Not By The People, was based on an income analysis of the 750 people currently appointed to public bodies, and the 2000-plus witnesses who gave evidence to Holyrood's committees over the past five years.
Although only 13% of Scots have incomes above £34,000, this group accounted for 67% of those giving evidence to committees and 71% of all appointments to public bodies.
In contrast, the 70% of Scots with incomes below the average salary of £24,500 accounted for 11% of public-sector appointments and just 3% of committee witnesses between 2007 and 2012.
The report concluded: "Scotland is run by people who pay higher-rate tax and they seek advice on how to run Scotland primarily from other people who pay higher-rate tax."
The Foundation said it had deliberately erred on the side of caution in estimating incomes, and the true disconnect between income and influence was probably worse than the figures suggested.
The report said recent scandals over the police, media and the banks have heightened concern over who influences over the political process.
It said: "Unequal access to power is as old as civilisation. But that does not mean it is acceptable or that it should go unchallenged.
"Restraining the power of money is one half of the equation; creating routes to power for those without money must also be part of the solution."
Bob Thomson, convener of the Foundation, said: "This really isn't good enough. Something has to be done to bring the bulk of the Scottish people back into political debate."
Larry Flanagan, chairman of the new fair access commission, said: "This report describes a Scotland of two peoples; one runs the country, the other just lives here.
"It is good for no-one if, as a nation, we put the opinions of the affluent, the powerful and the connected, above the voice of the majority. The Commission is eager to hear how people think we can improve this situation. Democracy is about more than simply voting twice a decade."
Stephen Reicher, professor of psychology at St Andrews University, said the problem with elites making decisions was that even good ideas risked provoking a backlash if people felt they were being "parachuted" into their lives.
He said a classic example was the healthy school meals initiative created by TV chef Jamie Oliver.
Reicher said: "To many it seemed a comment on their stupidity and even their lack of concern for the children. So they passed chips to these children through the school gates."
With regard to Holyrood, he said: "The skewed composition of quangos and those giving evidence to committees is wrong in practice as well as principle. It is unfair, it diminishes the quality of proposals. It makes good ideas less likely to succeed. It has no defence."
A Scottish Parliament spokesman said: "Tomorrow the equal opportunities committee meet gypsy travellers in Aberdeenshire and on Tuesday the welfare reform committee hears from people affected by benefit cuts.
"This demonstrates our commitment to hear from real people on real issues."