Changes to rules on social distancing could be delayed due to the Indian coronavirus variant, Boris Johnson's spokesman has admitted.
A review of the current "one-metre plus" social distancing advice, along with consideration of the possible introduction of coronavirus status certification, had been expected by the end of May.
Currently the government advises people to stay two metres apart from people they do not live with wherever possible, or to stay one metre apart while using additional safety measures such as masks.
When asked about the progress of the review, the prime minister's official spokesman said: "We want to do it as soon as possible but… we need time to assess the latest data on this variant first identified in India so I’m not going to give a set time for doing that.
“We want to do everything possible to give people enough time to prepare.”
A week ago, Johnson had said “we’ll be saying more later this month about exactly what the world will look like and what role there could be – if any – for certification and social distancing".
The reviews, announced by Johnson on 22 February, are separate to the government's "road map" out of lockdown for England.
The suggestion they could be delayed demonstrates the increasing concern about the spread of the B.1.617.2 variant of the virus, which was first identified in India.
The latest case data, released on Thursday, showed infections involving the variant in the UK had increased 152% in the space of a week, from 520 to 1,313.
Watch: 'Increasing confidence' vaccine works against Indian variant, says Hancock
On Friday, the PM told the nation the Indian variant – which is feared to be more transmissible than the Kent variant which caused the UK's winter crisis of widespread infections, hospitalisations and deaths – "could pose a serious disruption to our progress and could make it more difficult to move to step four [of lifting the lockdown] in June."
On Sunday, however, health secretary Matt Hancock said there is "increasing confidence" vaccines will protect against the variant, while warning it can "spread like wildfire" among people who haven't received a jab.
On Monday, the government proceeded with step three of its road map out of lockdown, easing restrictions in England to allow indoor mixing, the reopening of pubs and restaurants for indoor service and the resumption of international travel.
Johnson's spokesman, meanwhile, did not rule out a return to local restrictions to deal with the variant.
Asked whether ministers would consider the tiered system of rules seen last autumn, the spokesman would only say: "We don’t want to rule anything out".
“And I think until we have more data and more evidence, we won’t be making those judgments.”
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