The monthly Markit Household Finance Index found only 29% of those surveyed in March believed Brexit will be good for the economy.
Optimism has fallen sharply since last July, when 39% believed that leaving the EU would leave Britain better off. The number of households that expect the economy to worsen has increased from 42% to 53% over the same time period.
The survey also found that households in Scotland are the most pessimistic about Brexit’s impact.
“This survey shows that the reality of Theresa May’s hard Brexit is starting to hit home – and echoes the UK government’s own warnings that we would be left ‘permanently poorer’ outside the EU,” said SNP MSP Joan McAlpine.
“Theresa May agreed with that position. Ruth Davidson agreed with that position. Now the Tories are happy to risk jobs and household incomes by pursuing not just Brexit, but a hard Brexit outside the single market.
“This mounting concern over the economic impact of Brexit underlines the need for people in Scotland to have a choice over their future.”
Scottish ministers say there has been no clarity over how Scotland’s interests will be represented as the Brexit process gets under way, and the role the Scottish Government will play in negotiations.
Speaking during her visit to Scotland, Prime Minister Theresa May pledged Brexit would not mean the UK “stepping back from the world”, insisting she was aiming to build “a new partnership with Europe” while taking the opportunity to build “a more global Britain”.