The average estate agent branch had 62 registered sellers, building on the 60 registered in March, which was itself the highest number for six months.
The number of house hunters registering to look for property also increased from 274 in March to 277 in April.
The number of sales agreed across the month remained strong at eight, the same number as in March. Around 21% of sales were made to first time buyers (FTBs), down from 23% in March.
President of the NAEA, Gary Smith, said: "A major housing trend over the past six months has continued to be the relatively low numbers of sellers coming to market.
"For three months, however, the number of sellers has increased steadily. At the same time demand has stayed strong, as have the number of sales being agreed.
"The level of first time buyers has dropped slightly, and the NAEA will push hard for more measures to help this group from the new Government.
"It is good to note that any potential Conservative/Lib Dem pact will be able to agree on one thing at least, as both included the abolishment of Home Information Packs in their manifestos.
"All of the trends reported by our members point to reasonably sunny prospects for the summer housing market."
