According to independent research centre Merdeka Centre, Najib's overall ratings dropped from 69 percent in February to 65 percent in May 2012.
“This figure comes three weeks after the tumultuous events of the Bersih 3.0 demonstration and a series of other counter-demonstrations or events by supporters of the establishment,” it said in a statement.
Najib's ratings were pulled down by a massive 19 percent dip in Chinese support and an eight percent decline in Indian support.
According to the survey, the decline could not offset the commendable five percent rise in support from the Malay community.
The PM also saw a slight decline in support among voters aged under 40, with approval rates for those under 30 at a middling 61 percent.
However, Najib secured a comfortable 70 percent approval rating among respondents aged 50 and above.
Half of those polled still unhappy with government
Those earning more than RM3,000 a month appear to be losing faith in the prime minister, contributing an 18 percent drop in approval for Najib within this income group since February 2012.
However, the Bantuan Rakyat 1Malaysia (BR1M) appears to have won over the lower income group, with Najib's ratings climbing up four percentage points since February to an impressive 82 percent among those earning less than RM1,500 a month.
The polling centre also found that the relatively high approval rate enjoyed by the prime minister does not reflect how Malaysians feel about government performance.
Less than half, or 48 percent of the 1,019 respondents surveyed via telephone between May 10 and 18 were “happy with the government”.
This showed no improvement since February, with only a slight one percent rise seen among Malay voters who remained the most satisfied with the government among the communities polled, with 65 percent saying they are happy.