Brazil says the rate of deforestation in the Amazon increased by 28% between August 2012 and last July.
Provisional statistics from August 2012 to last July suggest that the deforestation area was 5,843 sq km, compared to 4,571 sq km in the previous 12 months.
A period of declining deforestation began in 2009.
The worst year on record was 2004, when 27,000 sq km of forest was destroyed.
Environment Minister Izabella Teixeira said she would set up a meeting with governors and mayors of the worst hit areas to discuss strategies to revert the trend, as soon as she returns from Poland, where she is attending a United Nations summit on climate change.