The development freeze, brought in at the end of 2006 to curb costs, means that core performance variables cannot be changed during a season – but there is scope to work on such things as fuels, lubricants, airboxes and exhaust acoustics.
Alonso believes rival teams have exploited the potential to find extra horsepower, while Renault has made virtually no progress since the freeze came into force.
He drew a contrast with Mercedes-Benz based on his experience with McLaren last season.
“When the engine [specification] was frozen two or three years ago, Renault more or less stopped development,” the former champion said in Thursdays press conference at the Hungaroring.
“There are less people working at the Viry factory in Paris and they are working just on building and maintaining the engines, nothing more than that – no research and no development.
“I was in another team last year and I know how much they improved the engine during the season and how many steps were introduced.
“Its the same for all the [other] teams: Every three or four races there is a little step in the engine that gives you some more horsepower.
“For Renault it hasnt been like that for the last two years, so there is a lack of power probably.”
Earlier this week Renaults team boss Flavio Briatore offered a more sinister explanation for why the French manufacturer has fallen behind in the horsepower stakes.
“The problem is that weve stuck to the letter of the current regulations on frozen engines, and weve been shafted,” Briatore told La Gazzetta dello Sport.
“Others didnt do that and are far ahead, while we are suffering.
“Its not fair.”