* Curve remains at four week lows after Brussels carbon rule
* Spot prices firm on tight supply, rising demand (Updates prices, adds quote, reference to EU decision, links)
FRANKFURT, July 25 (Reuters) - Europe's power curve traded at four-week lows on Wednesday after the publication of a European Commission plan to cut supply in the carbon emissions market.
The Commission said it proposed altering auction timetables for CO2 permits but did not give firm numbers. This was ahead of deeper reform to follow the attemped short-term fix.
"The market decided this was neutral to bearish and ignored an uptick in coal, oil and gas," one trader said.
Apart from fuels prices, Europe's power industry has to factor in the cost of mandatory CO2 avoidance efforts into prices, where the price of emissions allowances sets the benchmark.
German Cal '13 baseload was 5 cents lower at 47.70 euros ($58) a megawatt hour in the OTC market, the lowest since late June, having touched an intraday low of 47.50 euros.
The equivalent French OTC contract was 10 cents down on the day at 49.65 euros.
EU carbon for Dec 12 delivery was 5.6 percent down at 6.80 euros a tonne at 1331 GMT, as the CO2 market shrugged off the EU decision.
Crude oil rose slightly in the afternoon as concern about oil supply from the Middle East offset worries about oil demand from the euro zone which had set the tone earlier.
Prompt power prices rose for a third day due to low wind power production and tight French nuclear power availability.
Power for Thursday gained 90 cents in Germany to 48.65 euros and 15 cents in France to 49 euros, compared with day-ahead levels paid the previous day.
Midday peak-time solar capacity levels were expected to fall to near 10 GW by Saturday from nearly 20 GW currently utilised during midday peaks, while wind levels will remain at negligible levels up to the weekend, according to weather data.
Temperatures in Germany were at just under 30 degrees, having risen 3 degrees this week on average, while France saw level of over 30 degrees in the south and could spike at 35 degrees in some locations, boosting power demand for air conditioning.
German utility RWE postponed an investment decision on a 3 billion euro offshore wind farm in the North Sea to early next year because the liability rules for such projects are still unclear, according to a media report.
German business sentiment dropped in July for the third straight month in an Ifo survey but economists saw slight German growth in the second and third quarters.
Austrian utility Verbund said its earnings will drop this year if the economy keeps deteriorating. ($1 = 0.8275 euros) (Reporting by Vera Eckert; Editing by William Hardy)