HANOI Oct 26 - Vietnam's finance ministry has proposed doubling the country's annual coal export quota to reduce a mounting stockpile, after first rejecting a proposal to lower taxes on the fuel to boost domestic sales, a government news website reported on Wednesday.

Long-time net coal exporter Vietnam turned net importer last year as it held on to local output to help meet rising domestic demand, but cheap imported coal and a recent increase in natural resource taxes have hurt domestic sales, the report said.

Vietnam in July raised the national resource taxes for two different grades of coal to 10 percent and 12 percent, from 7 percent and 9 percent previously, and state-owned mining firm Vinacomin proposed to cut these taxes back down to regional levels of 5 percent and 7 percent.

But the finance ministry rejected Vinacomin's proposal, citing state budget concerns and the need for time to assess the new rates, the report said.

Instead the ministry proposed raising Vietnam's annual coal exports quota to 3 million-4 million tonnes for the years 2017-2020, from 2 million tonnes a year previously.

"This is a more feasible solution compared to cutting taxes as it can trim the stockpiles of coal that has low domestic demand while not affecting state budget revenue," the ministry said in a statement posted by Vinacomin on its website.

Vinacomin, or Vietnam National Coal-Mineral Industries Holding Corporation, said it produces from its Vang Danh, Uong Bi and Nam Mau mines 8.5 million tonnes of coal a year, about 3 million tonnes of which are grades that are not used domestically, according to the government report.

Vietnam's coal exports last year plummeted 75.9 percent from 2014 to 1.7 million tonnes, while imports surged 123.8 percent to 6.9 million tonnes, customs data showed.

Imports of the fossil fuel in the first nine months of this year jumped 147.6 percent to 10.5 million tonnes, well above a full-year import forecast of 3.1 million tonnes by the trade ministry, the data showed.