PARIS, April 12 (Reuters) - Successive cold snaps in the past week have destroyed between 30,000 and 50,000 hectares of French sugar beet, growers group CGB said on Monday, calling it the worst frost-related losses for the sector ever recorded.

The estimate is higher than the 10,000-40,000 hectares of recently sown sugar beet that the CGB estimated last week would need replanting.

Sugar beet plantings had already been expected to fall this year after pest attacks last year caused jaundice disease to ravage crops and as farmers have cut back on the crop in recent years due to weak sugar prices.

"These frosts just a few months after the jaundice constitutes a new disaster for beet growers and weakens certain production areas as well as our industrial tools," CGB Chairman Franck Sander said in a statement.

Rapeseed plantings, vineyards and orchards have also been damaged, prompting the government to promise financial aid for farmers.

"Negative temperatures are still expected in the coming days. The final diagnosis remains to be clarified, but the conclusion is already clear: the French beet industry has never experienced such losses due to frost!" the CGB said.

Legislation that reauthorised neonicotinoid pesticides to protect sugar beet from disease, after they had been banned to protect bees, forbids farmers to replant seeds treated with neonicotinoids. (Reporting by Sybille de La Hamaide. Editing by David Evans and Mark Potter)