Thailand has pledged to renew its rice-buying scheme for a third year, defying opposition over a policy that has been blamed for straining government finances and slashing exports as the grain has piled up in warehouses

The two-year old programme to pay farmers more for rice than it is worth on international markets has cost Thailand its spot as world's top exporter and provoked concern at the World Trade Organization.

The government has spent 410 billion baht ($13.70 billion) in buying paddy since the scheme kicked off in October 2011, and has been looking at measures to stem ballooning losses so far estimated by analysts and industry officials to be at least $6 billion.

The government has said that has sold up to 7.3 million tonnes of rice from stocks to foreign governments, including China, Bangladesh and the Philippines. However, all buyers have denied the deals and traders said activity at ports did not suggest big deliveries.

Thailand pays farmers 15,000 baht a tonne of paddy, or around 50 percent above market prices, pushing Thai export prices for common grade white rice to $550 a tonne, or around $170 per tonne higher than the offers from India, Vietnam and Pakistan.