Spain’s Health Ministry on Tuesday defended changes to its methodology for recording coronavirus data that have led to wild fluctuations in daily statistics and provoked sharp criticism by opposition parties.

On Monday the government revised down the country’s overall death toll from the epidemic by nearly 2,000, and while Tuesday’s reported cumulative toll of 27 117 was 283 higher than Monday’s, the ministry said just 35 people had died from the disease over the past seven days.

Health Emergency Coordinator Fernando Simon attributed the difference to old cases, which were included retrospectively as authorities adjust to a new tracking system and check back over historical data provided by regions.

“The process is going to continue for several days,” he said.

Confirmed cases of the virus rose by 859 to 236 259.

Government spokeswoman Maria Jesus Montero said adjusting the methodology could distort statistical analyses, but that the new system was necessary to track the disease’s progress through the population.

“It is absolutely essential for us to know today how this disease is being transmitted,” she told a news conference.

Pablo Casado, leader of the main conservative opposition People’s Party, accused the government of hiding the true death toll and said the tweaking showed “an intolerable lack of respect.”

One of the European countries worst-hit by the virus, Spain has begun to unwind astrict lockdown that helped curb its spiraling infection rate and brought its economy to a grinding halt.

Criticism of the left-wing government’s handling of the crisis has boiled over into street protests in parts of the politically polarized country.