Mr Blackford condemned the “violation” of Mr Johnson’s privacy but added a “senior Conservative source in Downing Street” was reported to have said the “finger of blame for all this getting out is being pointed at the SNP, particularly Ian Blackford who is local”.
The prime minister insisted his Government has not been blown off course by Covid-19 - but acknowledged that “sometimes it is necessary” to change direction in “response to the facts as they change”.
“We’d like to be in a Government that has the impression of being competent – rather than lurching from one issue to another and then after a short time doing a U-turn.”
Sir Charles Walker, deputy of the 1922 committee of Conservative backbenchers, said it was becoming increasingly difficult for MPs to defend the government - as policies can be quickly dropped by ministers.
Labour accused Johnson of trying to shirk responsibility for a “shambles” caused by the “incompetence” of his government.
The U-turn comes after it was announced that secondary students in Scotland will have to wear face coverings in school corridors and communal areas from Monday.
His comments come as the Education Select Committee announced that Gavin Williamson will appear before them on September 16.
Boris Johnson will not start randomly drug testing members of his Cabinet, despite Shaun Bailey - the Tory candidate for London mayor - saying he would urge all major companies in the capital to do so.
"He has mired himself in scandal, lies and corruption (not to mention racism, misogyny and homophobia) throughout his political life and now has the audacity to drive us headlong into the brick wall of a distastrous no-deal Brexit."