Three quarters of people are unable to name their MP, according to an annual Hansard Society survey.
Interviews with 1,128 people found that 22% of people could name their own MP, compared with 38% in 2011.
The report suggests many people were "disenchanted" with politics, with the proportion saying they would not vote doubling from 10% in 2011 to 20%.
The public's self-declared likelihood to vote is the lowest recorded since the audit series began 10 years ago.
Despite the prominence of the eurozone crisis and the debate on the UK's EU membership, 57% of people did not correctly identify the fact that Britons elect members to the European Parliament.
The report from the Hansard Society - a charity which aims to strengthen parliamentary democracy and encourage greater public involvement in politics - also suggests that 33% of people believed peers were elected.
The society said "fewer and fewer people are convinced about the value of voting than at any point in the last decade", raising "serious questions" about the system of government in this country.
The survey suggests:
- 41% of the public say they are certain to vote in the event of a general election, compared with 48% last year and 58% two years ago
- 12% of 18-24 year olds say they are absolutely certain to vote - down from 22% last year and 30% two years ago
- 58% of people are still not prepared to vote even "if they felt strongly enough about an issue"
- 23% are satisfied with the way that MPs generally are doing their job - compared with 29% in 2010.
Some of the figures bucked the trend and revealed closer engagement:
- 47% of the public say they would like to be involved in local decision-making - up from 38% from last year
- 47% also agree that Parliament "holds government to account" - again up from 38% last year.
Dr Ruth Fox, director of research at the Hansard Society, said: "These results, coming on top of the low election turnouts last year, should be an urgent warning to all the political parties."
She added: "The public's improved view of Parliament can perhaps be explained by the increased profile of select committee activity in tackling issues such as phone-hacking and taxation of multinational corporations."