Millionaires are souring on the stock market, reporting their lowest level of confidence in stocks in over a year.
The Spectrem Millionaire Investor Confidence Index, compiled by Spectrem Group, fell to its lowest level in 16 months, sliding to 6 from 15. The reading indicates that millionaires have gone from bullish to neutral. The survey also showed that millionaire plans to invest in stocks fell to their lowest level since the financial crisis.
Read MoreIncomes rise for bottom 99%
According to Spectrem, the main reason confidence fell among millionaires was the Fed and the prospect of rising interest rates.
"For the past few years, millionaire investors have expressed concern about the economy and markets being artificially supported by low interest rates," said George Walper, president of Spectrem Group. "With the Fed indicating that interest rates will be increased this year, millionaires are not as optimistic about their household income and assets."
The survey was taken between June 18 and June 24, so it doesn't include the impact of the most recent flare-up in Greece, which could further dampen millionaire confidence.
Read MoreMillionaires lack estate plans
When asked about the most serious threat to their investments, the largest number of millionaires pointed to the stock market (17 percent), while 13 percent said the economy, and 12 percent said the political climate.
When asked how they plan to invest in the coming months, millionaires largely plan to stay on the sidelines. The measure of millionaire intent to invest in stocks fell to its lowest level since April 2009. Their intention to invest in bonds dropped to the lowest level in the indices' 11-year history.
"Millionaires indicated a significant retreat from investing in stocks," the report said.