Prime Minister Boris Johnson has been warned by scientists that separate households meeting under one roof is a main contributor to a sudden increase in Covid-19 cases.He is believed to have been advised that putting an end to “support bubble” rules which allow the public to visit each other at their respective homes may need to be axed as a consequence.Current rules allow up to 30 people from two households to meet indoors – with the measure only coming in to effect last month when lockdown began to ease.However, the Office for National Statistics revealed last week that cases of coronavirus patients testing positive for the disease had hit 4,200 per day at the end of July – more than double the 2,000 positive results per day recorded at.