The large South American country, which usually has Latin America's second-highest human development index and gross domestic product, will contract into 2 percent to 3 percent negative economic growth this year, the analysis for the Financial Times found.
The negative-growth forecast contrasts sharply with official figures, which predicted 1.88 percent annual growth for May.
"The government will continue to report positive year-on-year growth ... but there's broad consensus that Argentina is currently going through an acute downturn," David Duarte, Latin American economist with the New York market analysis firm 4Cast, told the Times.
Much of the blame for the discrepancies, and resulting market concerns, lies in alleged manipulation of official economic data by President Cristina Fernandez de Kirchner's administration, the newspaper said.
At the center of the controversy is Argentina's National Statistics and Census Institute, known as Indec, responsible for collecting and processing statistical data.
The Times calls Indec "discredited" and says investors and others "remain dubious of official inflation figures."
Indec said June inflation was 5.3 percent. The the private-sector analysts the Times consulted say the inflation rate is 12 percent to 15 percent.