Deforestation in Brazil's Amazon basin dropped by 18 percent over the past year, the government said Wednesday, but the official figures were at odds with a conservation group's findings.

Environment Minister Izabella Teixeira said deforestation from August 2013 to July 2014 totaled 4,848 square kilometers (1,870 square miles), the second-lowest figure on record.

But a non-government group, Imazon, last week warned of a 467-percent rise in October from the same month a year earlier, basing its calculations on data collected with the help of Google Earth.

Teixeira insisted the official estimate was the most accurate.

"Anything else is speculation. We have been working hard to end deforestation," she said.

"There are systems such as those of Imazon speculating on an increase. Now there is an official figure. I do not want to suggest others are not capable of monitoring the situation, but we cannot mix either methods or information," Teixeira said.

She presented the government figures just days before the Lima Climate Change Conference, which opens Monday.

Teixeira said the government had made significant recent progress on "preventive control," tightening regulations and increasing public awareness of the issue to cut deforestation by 83 percent since 2004.

Imazon responded by saying it had concerns about the official data, which "throw into some doubt the effectiveness of current prevention and deforestation control policies."

The organization's own estimate suggested a loss of the equivalent of 24,000 football pitches.

The government measure covers Brazil's nine Amazonian states using the Brazil's Space Research Institute's satellite forest clearing detection service PRODES.

Greenpeace Brazil's Amazon director Paulo Adario told AFP the government figures comprised some "good news."

But he added: "There is nothing to celebrate as we are nowhere near zero deforestation.

"We were all concerned as the downward trend was interrupted last year. It seems that may have been just a blip," Adario said.

The 2011-2012 figure of 4,571 km2 was the lowest on record. Although the following year saw a 29 percent increase to 5,891 km2, official sources insist the underlying trend now is downward.

Brazil recently announced it was adopting a new satellite alert system to counter deforestation in the Amazon, the world's largest forest, which peaked at 27,000km2 in 2004.

Adario said the latest figures confirm Brazil does not have to resort to deforestation in order to bolster food production.

"Brazilian production of cereals has gone up in the past few years. So has that of beef and Brazil is one of the world's biggest (foodstuffs) producers.

"The idea you have to choose between protecting the environment and producing foodstuffs is false," he stressed.