* Slowest quarterly GDP rise in six years

* Government revises down 2008 growth to 6.8 pct (Adds analyst, background on data doubts, details on sectors)

By Lucas Bergman

BUENOS AIRES, June 18 (Reuters) - Argentina's gross domestic product expanded 2.0 percent in the first quarter compared with the same period a year ago, the smallest growth rate since late 2002, the government said on Thursday.

The INDEC national statistics agency, which many private analysts accuse of overestimating growth, also said the first-quarter GDP marked 0.1 percent growth over the fourth quarter of 2008, narrowly avoiding a technical recession of two consecutive quarters of contraction.

INDEC said activity in the manufacturing sector fell 3.2 percent in the first quarter from the same period a year ago, while the service sector expanded by 4.7 percent.

Consumer activity, which represents about 65 percent of the country's gross domestic product, rose 1.5 percent year-on-year but investment sank 14.2 percent due mainly to falling investment in construction and capital goods.

Argentina's economy has grown by at least 6.8 percent in each of the last six years ARECI12, but the global recession and political uncertainties have hit factory output and consumer spending.

President Cristina Fernandez, who faces a key mid-term election on June 28, has said Latin America's No. 3 economy will continue to grow this year, refuting private forecasts for a contraction.