By Susanna Twidale and Ron Bousso LONDON (Reuters) -British finance minister Jeremy Hunt said on Thursday the government would increase a windfall tax on oil and gas firms and extend it to power generation firms as he seeks to raise money to plug a major hole in the public finances. Soaring oil and gas prices in the wake of Russia’s invasion of Ukraine have sent household energy bills to record highs, triggering Britain’s worst cost of living crisis in generations. Hunt said the levy on oil and gas companies would be increased to 35% from its current rate of 25% and extended until the end of M…