Ministers want all over 50s to have received a second coronavirus jab before a further easing of lockdown restrictions on 21 June.
The move comes amid growing fears over the new highly transmissible strain of the disease first identified in India.
The government is coming under increasing pressure from experts to consider a delay to its 21 June deadline.
Linda Bauld, professor of public health at the University of Edinburgh, today said the date was “too early”.