UK GAS-Prices plunge as 2017 coal, carbon and power turn bearish

* Prompt gas contracts fall more than 5 percent

* Strong supply, weak demand break spell of price gains

* Other power plant commodities also tail off

Jan 3 (Reuters) - UK prompt gas prices plunged on Tuesday, the first full trading day of 2017, as weak demand and ramped-up North Sea supply wiped out more of last month's gains, matched by sell-offs on European coal, carbon and power markets.

Trading in 2017 got off to a bearish start with the exception of Brent crude oil, rising to $58 a barrel amid hopes for production cuts, even as power plant fuels faced sharp selling pressure.

The price of gas for instant delivery fell by 3.15 pence or 5.95 percent to 49.75 pence per therm by 0943 GMT, having seen a near two-week run of gains that ended on Monday when a select few prompt contracts traded.

Britain's gas market was oversupplied by 31.4 million cubic metres per day (mcm/day) as domestic output from the North Sea fully recovered from a spate of short-lived outages last month.

Daily gas demand is pegged at 321.9 mcm/day, according to National Grid (LSE: NG.L - news) , and is below analysts' expectations as milder weather has reduced the need for heating.

Gas for Wednesday delivery also fell by 3.15 pence or 5.95 percent to 49.75 pence per therm.

Related commodity markets were dragged lower on Monday, with benchmark European carbon prices down 5.05 percent at 5.83 euros a tonne.

The leading API2 2018 coal contract was 2.05 percent lower at $63 a tonne, while volatile French and German day-ahead power prices registered double-digit losses, helped by rising wind power supply.

Supplies from the UK Continental Shelf were strong following patchy output from terminals including St. Fergus Shell, St. Fergus Mobil and Bacton in December, Thomson Reuters (Dusseldorf: TOC.DU - news) analysts said.

However, Norwegian gas capacity will be reduced by 8.3 mcm for Tuesday due to an outage at the Sleipner gas field. There was no sign yet of any effect on supplies.

Flows through Norway's Langeled pipeline to Britain were running at peak capacity of around 74 mcm/day.

In the Netherlands, the day-ahead gas price at the TTF hub was 0.50 euro lower at 18.90 euros per megawatt-hour. (Reporting by Oleg Vukmanovic; Editing by Dale Hudson)