LONDON—The British government has asked public sector managers to test their contingency plans against a worst-case scenario of 25 percent staff absence as part of efforts to minimise disruption from the rapid spread of the Omicron variant of the coronavirus. With daily infection numbers at a record high and people who test positive required to self-isolate for at least seven days, the government expects businesses and public services to face disruption in the coming weeks, it said in a statement. “So far, disruption caused by Omicron has been controlled in most parts of the public sector, but public sector leaders have been asked to test plans against worst-case scenarios of workforce absence of 10 percent, 20 percent, and 25 percent,” it said. Prime Minister Boris Johnson has asked ministers to work closely with their respective sectors to develop robust contingency plans, said the Cabinet Office, which is coordinating the government’s …