The transport secretary defended the decision as a “safety-first” approach.
Mr Shapps told BBC News: “I want to be straight with people, it’s actually a difficult decision to make, but in the end, we’ve seen two things really which have caused concern.
“One is that the positivity rate has nearly doubled since the last review in Portugal, and the other is that there’s a Nepal mutation of the so-called Indian variants which has been detected.”
He added: “We just don’t know the potential for that to be a vaccine defeating mutation and simply don’t want to take the risk, as we come up to June 21.”
With so much uncertainty surrounding whether or not other popular holiday destinations will make the green list in future, experts have cited caution over exchanging travel money.