A high proportion of new Labour party members are part of a well-paid urban elite and the party is struggling to attract people from rural areas, the elderly and the poor, internal data has shown.
The leaked report, commissioned internally, and sent to Labour's national executive committee, shows that a significant number of those who joined the party since the 2015 election defeat were "high-status city dwellers".
It added that there were fewer traditional supporters from poorer parts of society who were members, which will fuel criticism that the party is moving away from its roots.
The report's summary, leaked to The Guardian, warns: "Groups which are over-represented as Labour party members tend to be long-term homeowners from urban areas (particularly inner city areas) who have high levels of disposable income."
It found that "high-status city dwellers" who make up 4% of the general population, now make up 11.2% of party membership. Meanwhile, families "who have to budget to make ends meet", make up 4% of membership, in comparison with 8.7% of the UK's population.
"Those who are under-represented tend to be either young singles/families who rent properties on a short-term basis and require financial assistance or those who live in rural communities," The Guardian reported.
However the party's membership continues to rise across all sectors of society since Jeremy Corbyn became leader. The document shows that at the end of 2015, Labour's membership stood at 388,103 – up 194,349 on the 2014 figure and the largest number since 1998.
The document also shows the dissatisfaction in some quarters with Corbyn, and that there have been 6,627 resignations from the party this year – twice the usual number.
Lord Watts, the former leader of the parliamentary party, told the House of Lords in January: "My advice to my own party leadership is that they should take less notice of the London-centric, hard-left political class who sit around in their £1m mansions, eating their croissants at breakfast and seeking to lay the foundations for a socialist revolution.
"It is not the job of the parliamentary Labour party to sit around developing ultra-leftwing policies that make it feel good. It is its job and responsibility to come forward with policies that will help us win the next general election."