Nearly 90% of financial firms think the chance of a "high-impact" event happening in the next year - such as the collapse of the euro - has risen in the last six months, the Bank of England said.
The likelihood of such an event - which could also include a credit rating downgrade for the UK - happening in the short term is at the highest level since 2008, the Bank's survey said.
Elsewhere, the poll found that 59% of its respondents, which include banks, hedge funds and building societies, are less confident than in January to June.
The threat of the eurozone debt crisis was the most commonly cited risk, with the economic downturn, funding risks and risks around regulation in the top five.
The Bank conducts the survey to monitor financial stability in the UK and to identify risks.
Nearly 70% of participants thought the chance of a high-impact event occurring within one to three years - had increased.
Some 76% of respondents flagged sovereign debt risk as the biggest threat, while 76% also raised the risk of economic downturn as a serious problem.