LONDON, Dec 31 (Reuters) - More than 2 million people in Britain tested positive for COVID-19 in the week before Christmas, Office for National Statistics (ONS) estimates published on Friday showed, with the highest ratio of around one in 25 people seen in England. Britain is experiencing a surge in cases of the virus driven by the highly-transmissible Omicron variant, but the government is hoping its comprehensive vaccine programme and potentially milder disease caused by Omicron will allow it to keep the economy largely open. The ONS estimates are modelled based on survey data. Friday"s estimates, which covered the week to Dec. 23, showed the ratio of people with COVID in England rising to one in 25, from one in 35 between Dec. 13 and Dec. 19. The latest estimated ratio in Wales, Scotland and Northern Ireland were around one in 40.