Jan 6 (Reuters) - Perth Mint's gold product sales in December eased from the previous month but robust investment demand for the safe-haven metal led average monthly 2020 shipments to double from the prior year, the refiner said in a blog post on Wednesday.

Sales of gold coins and minted bars dropped to 76,806 ounces last month, declining 8.7% from a seven-month high reached in November and by 2.7% from a year earlier.

Sales of silver coins also slid 15.8% to 941,767 ounces in December, their lowest since May, and 30.8% lower than the same month a year ago.

Despite the decline, Perth Mint said overall sales in 2020 were strong, with average monthly sales of minted products rising by 100% for gold and 42% for silver, compared with 2019.

"The Perth Mint saw strong investor demand across its entire suite of precious metal products in 2020, with sales of minted products and inflows into The Perth Mint Depository rising notably," said Jordan Eliseo, Manager Listed Products and Investment Research.

Tailwinds from rising inflation expectations, record low yields and low interest rates for years to come, indicate that demand for gold, and therefore gold prices, is likely to remain well supported as we move through 2021, he added.

Gold prices climbed 25% in 2020, recording their best year in a decade as large stimulus measures by governments and central banks to cushion the blow of the virus boosted demand for the metal, which is seen as an inflation hedge.

The Perth Mint, owned by the government of Western Australia, refines more than 90% of the newly mined gold in Australia, one of the world's top gold producers.

(Reporting by Nakul Iyer and Diptendu Lahiri in Bengaluru, additional reporting by Swati Verma; Editing by Ramakrishnan M. and Louise Heavens)