The sheer dominance by the top two social classes of Oxford and Cambridge University admissions has been revealed in newly released data.
Four-fifths of students from England and Wales accepted at Oxbridge between 2010 and 2015 had parents with top professional and managerial jobs, and the numbers have been edging upwards.
The data, obtained by David Lammy MP, also shows a "shocking" regional bias, with more offers made to Home Counties pupils than the whole of northern England.
Mr Lammy said he was "appalled to discover" Oxbridge is actually moving backwards in terms of elitism.
Unveiling the data, he described the universities as the "last bastion of the old school tie" and highlighted stark regional divisions.
Nationally about 31% of people are in the top two social income groups. They are the doctors, the lawyers, the senior managers.
The data reveals these top two social classes cleaned up in terms of places, with their share of offers rising from 79% to 81% between 2010 and 2015.
This was despite both universities spending £5m each a year on efforts to cast the net wider for students, according to official figures.
The data on admissions by region provided by the universities themselves showed:
- More than a quarter of Cambridge offers went to eight local authority areas
- Just under a quarter of Oxford offers went to eight local authority areas
- London and south-east England received 48% of offers from both Oxford and Cambridge
- The Midlands received 11% of Oxford offers and 12% of Cambridge offers
- The North West, the North East, Yorkshire and the Humber between them received 15% of Oxford offers and 17% of Cambridge offers
- Oxford made about 100 offers to students in the whole of Wales last year
The University of Cambridge made nearly 2,953 offers to four home counties, and 2,619 offers to the whole of the north of England.
Whereas Oxford made 2,812 offers to applicants in five home counties and 2,619 to students in the whole of northern England.
Applications were, however, significantly higher from both the counties surrounding London and around the universities themselves.
A spokesman for Cambridge said its admissions were based on academic considerations alone, adding that the greatest barrier to disadvantaged students was poor results.
"We currently spend £5m a year on access measures leading to 190,000 interactions with pupils and teachers."
An Oxford spokesman said: "We absolutely take on board Mr Lammy's comments, and we realise there are big geographical disparities in the numbers and proportions of students coming to Oxford.
"On the whole, the areas sending few students to Oxford tend also to be the areas with high levels of disadvantage and low levels of attainment in schools.
"Rectifying this is going to be a long journey that requires huge, joined-up effort across society - including from leading universities like Oxford - to address serious inequalities."
Mr Lammy said the scale of the regional divide went far beyond anything he could have imagined.
He accused Oxbridge of failing to live up to its responsibilities as national universities, saying: "Oxbridge take over £800m a year from the taxpayer - paid for by people in every city, town and village.
"Whole swathes of the country - especially our seaside towns and the 'left behind' former industrial heartlands across the North and the Midlands are basically invisible.
"If Oxbridge can't improve, then there is no reason why the taxpayer should continue to give them so much money."
Mr Lammy added: "Whilst some individual colleges and tutors are taking steps to improve access, in reality many Oxbridge colleges are still fiefdoms of entrenched privilege, the last bastions of the old school tie."
He called for a centralised admissions system to be introduced at the universities and for Oxbridge to communicate more directly with talented students by writing to all straight A students to invite them to apply.
By Branwen Jeffreys, BBC News education editor
We should all care who goes to our top universities because they end up running the country.
Less than 1% of the adult population graduated from Oxford or Cambridge, but the two universities have produced most of our prime ministers, the majority of our senior judges and civil servants, and many people in the media.
So surely it's good news that more of their students are from state schools?
As this research shows, that's only part of the story. The home counties of southern England are significantly wealthier than the north. You just have to look at how many children are from families earning so little their children qualify for free school meals.
In Buckinghamshire it's just 5.5% of pupils, in Surrey 6.8%. Travel north to Middlesbrough and it reaches 27.9%, and Rochdale 20.5%