The British public is increasingly sceptical that everyone has the same opportunity to do well in life, a poll for the Sutton Trust suggests.
The survey found just two-fifths (41%) agreed that people had equal chances to get ahead, compared with more than half (53%) who said the same in 2008.
Almost half (46%) of those polled said today's youth would have a worse life than their parents' generation.
The government said it was committed to making the country "work for everyone".
The survey asked 2,001 adults across Britain aged 16 to 64 what they thought was needed to help someone get on in life and found:
- seven in 10 (70%) thought that knowing the right people was important, with a further 19% saying it was essential
- having a good education was considered important by 68% and essential by 28%
- having well-educated parents was viewed as important by 64% and essential by 6%
- 60% thought that having ambition was important, with a further 36% saying it was essential
- 50% placed importance on coming from a wealthy family, with 8% saying this was essential
The survey also found that almost half (47%) thought high-quality education in comprehensive schools would most help those from disadvantaged backgrounds to get on in life, while 23% thought that lower university tuition fees would help.
The findings come as research commissioned by the Sutton Trust finds that improving social mobility could boost the UK's GDP by almost £600 per person per year.
Research by economic consultancy Oxera for the Trust assessed levels of social mobility in different European countries, looking at issues such as individual income, parents' education and how well a person's job matched their skills.
It concluded that bringing social mobility in the UK up to the average for western Europe would lead to an annual increase in GDP of £590 per person.
Sutton Trust chairman Sir Peter Lampl said Britain had very low social mobility compared with other countries.
"Our research shows that if social mobility were brought up to the western European average, GDP would increase by 2.1%, equivalent to a monetary value of £39bn.
"There is also a low and declining percent of the public (from 43% in 2003 to 29% in 2017) who believe today's youth will have a better quality of life than their parents.
"The government should make improving social mobility a top priority.
"Alongside other initiatives there needs to be a concerted effort to improve early years provision, provide fairer access to schools and universities and address the numerous social barriers which exist."
A Department for Education spokesman said the government was committed to making sure Britain was a country that worked for everyone.
"We want to make sure everyone can get a world-class education at every stage of their life, and go as far as their talents will take them, whatever their background.
"There are 1.8 million more pupils in good or outstanding schools than in 2010, more disadvantaged students than ever before attending university and we are investing an additional £500m a year into high quality technical education.
"We will also be building on the progress of our £72m opportunity areas programme, which is bringing together local businesses, schools and councils in 12 social mobility 'coldspots' to create better opportunities for young people."