The survey carried out among voters in peninsular Malaysia between April 28 to May 2 also placed Pakatan Rakyat ahead of BN in terms of the favoured party to form the government.
Najib's popularity has taken a slight dip from 64 percent when the last poll was conducted in March, to 61 percent now just days before the country heads to polls.
Merdeka Centre said that the figure reflects the slide in the "feel good" factor that was previously generated by the large-scale distribution of Bantuan Rakyat 1Malaysia (BR1M) and also other forms of cash handouts.
Concerns over the economy topped the list of issues that voters wanted to hear being discussed, at 25 percent.
Marginal seats will decide winner
Based on the survey results, Merdeka Center said that the emerging victor in the election will be determined by which side manages to snag a larger pie from the 46 marginal parliamentary seats across the country - all of which fall within a 3 percent vote-shift margin.
Thirty-four of the marginal seats are located in peninsular Malaysia while six each are in Sabah and Sarawak.
Apart from the marginal seats, the centre predicts that BN will win an estimated 81 parliamentary seats while Pakatan will win an estimated 89.
The survey was carried out among 1,600 registered voters via telephone interviews, with 59 percent of respondents being Malay, 32 percent Chinese and 9 percent Indians.