Well-off parents create a "glass floor" for their less academically inclined children ensuring they "hoard the best opportunities" over poorer peers, a study has suggested.
Children from wealthier families but with less academic ability are 35% more likely to become high earners than their more gifted counterparts from poor families, according to findings from the Social Mobility and Child Poverty Commission.
The study, entitled "Downward mobility, opportunity hoarding and the 'glass' floor", looked at the lives of 17,000 people born in Britain in the same week in 1970.
The potential for success can even date as far back as the social background of the child's grandfather, the report suggested.
Factors influencing a child's success later in life included the level of their parents' education, the type of secondary school they attend and the highest qualification they achieved, the report said.
Wealthier parents often help their children by using their social networks and finding them useful unpaid internships. They may also provide better careers guidance and focus on so-called soft skills including self-confidence and leadership.
On examining the participants' achievements by the age of 42, the report found "high attaining children from less advantaged family backgrounds are less able to, or at least less successful, at converting this early high potential into later labour market success".
The report indicated those highest up the social ladder may have to make way for others as attempts are made to increase social mobility.
It said: "If policy makers are determined to increase social mobility in a climate where 'room at the top' is not expanding then the factors that limit downward mobility will need to be addressed."
The report suggested a number of ways to tackle the issue, including ending unpaid internships, improving the quality of schools in disadvantaged areas, and educating parents to improve their skills and perspectives.
Study author Dr Abigail McKnight from the London School of Economics said: "The fact that middle class families are successful in hoarding the best opportunities in the education system and in the labour market is a real barrier to the upward social mobility of less advantaged children."
"Children from less advantaged families who show high potential at age five are struggling to convert this potential into later labour market success."
"Schools could do much more to help children from less advantaged families build on high early potential."
Commission chairman Alan Milburn said the findings highlighted a "social scandal".
"It has long been recognised that there is a glass ceiling in British society that prevents children with potential progressing to the top. This research reveals there is a glass floor that inhibits social mobility as much as the glass ceiling.
"It's a social scandal that all too often demography is still destiny in Britain. The Government should make its core mission the levelling of the playing field so that every child in the country has an equal opportunity to go as far as their abilities can take them."