Mr Johnson wrote to all opposition party leaders asking them to a briefing this week.
He wrote: “Coronavirus is the biggest threat this county has faced in decades – and we are not alone. All over the world we are seeing the devastating impact of this invisible killer.”
Mr Johnson added that party leaders have a duty “to work together”.
Tory party chairman Amanda Milling said Sir Keir must put aside any remaining party differences in the coming months.
She said: “I call on Keir Starmer to put aside the divisiveness and infighting that has plagued the top of the Labour Party for the last five years, and work with the government to support the national effort.
One senior Labour figure even suggested that the PM should soon invite Starmer and the party’s health spokesperson into Cabinet meetings to show true unity.