The within-day contract was down 0.4 pence at 23 p/therm by 0851 GMT.
The day-ahead contract slipped by 0.45 pence to 22.8 p/therm.
Traders said that lower gas power demand left the system oversupplied while expectations of a likely increase in liquefied natural gas (LNG) shipments to Europe, with Chinese demand weakened because of the coronavirus, also weighed on curve prices.
Britain's gas system was oversupplied by 21.8 million cubic metres (mcm), with demand forecast at 279.8 mcm and flows at 301.6 mcm/day, National Grid data showed.
Peak wind power generation is forecast at 12.7 gigawatts (GW) on Friday and 13.3 GW on Saturday, Elexon data showed.
Analysts at Refinitiv forecast demand for gas from power stations at 46 mcm on Friday and 31 mcm for Monday, down 29 mcm and 17 mcm respectively from previous forecasts.
LNG prices have hit record lows this week and traders have rushed to find alternative destinations for tankers after Chinese buyers rejected shipments because of the coronavirus epidemic.
"UK and wider Northwest Europe may have to absorb even more cargoes in later February ... If strong LNG sendout persist, (the) UK could have spare supply to export to the continent or inject into (storage)," Refintiv anbalysts said in a daily research note.
The March contract was down 0.3 pence at 22.02 p/therm
The day-ahead gas price at the Dutch TTF hub was down 0.24 euros at 9.03 euros per megawatt hour.
The benchmark Dec-20 EU carbon contract was down 0.11 euros at 23.45 euros a tonne.