LONDON, Dec 13 (Reuters) - Shopper numbers across Britain fell 1.1% in the week to Dec. 11 versus the previous week, driven by a 2.7% drop in activity on high streets as new COVID-19 restrictions spooked shoppers, researcher Springboard said on Monday. It said that whilst the government"s COVID-19 "Plan B" restrictions for England did not come into full force until Monday, they appeared to have had an impact last week. Springboard"s Central London "Back to the Office" benchmark, which covers areas in close proximity to offices, declined 5.3% versus a 3.0% decline in shopper numbers for Central London as a whole. Footfall fell 1.6% in other regional cities, but was up 1.5% in market towns which have smaller, more local high streets, Springboard said. Britain first expressed concern about the new Omicron coronavirus variant on Nov. 25. On Dec. 9, Prime Minister Boris Johnson imposed tougher COVID-19 restrictions in England, ordering people to work from home, wear masks in public places and use vaccine passes to slow the spread. read more Springboard said the gap in overall footfall from the 2019 level was 17.7% last week, but footfall was 18.1% above 2020.