Eleven Conservative MPs have called on Welsh ministers to explain the “scientific basis” behind the decision to allow more activity outdoors – but only locally.
On Monday people in Wales were given the right to go outdoors and meet others from another household.
But they can only be within their local area – five miles as a “general rule”.
The Welsh Government said any changes to lockdown are based on the latest “scientific and medical advice”.
First Minister Mark Drakeford said the decision aimed to reduce the risk of coronavirus spreading.
The five-mile guidance has been heavily criticised by Senedd Welsh Conservatives, who have accused the Welsh Government of ignoring the needs of rural communities.
Scientific advisors to the Conservative UK government have expressed concern at the speed lockdown is being eased in England. In England, the UK government has allowed for unlimited travel and for groups of six to meet.
A letter penned by Ynys Mon MP Virginia Crosbie, and signed by all Welsh Tory MPs barring the Welsh Secretary Simon Hart and Wales Office minister David TC Davies, asked for the scientific basis for the travel rule and interpretation of it “given that in England there is no restriction on how far you can travel”.
It asked if “delays in linking up to the UK testing portal and delays in rolling out Wales’ own track and trace digital platform impacted the reluctance to lift measures”.
Contact tracing began on Monday, although an IT system to support it will not be in place until next week.
The letter also asked if any assessment had been done of the public health impact of an “overextended lockdown” in Wales, and of any mental health and educational impacts from delaying reopening the economy.
Ms Crosbie said: “As a former scientist, I appreciate just how much the evidence needs to inform decision-making, especially at such a crucial time for people’s health in Wales.
“However, when decisions made in Wales are markedly different to those in England, it is only fair that people in my constituency of Anglesey and across Wales understand the evidence upon which those conclusions were arrived.”
Plaid Cymru Arfon MP Hywel Williams said Welsh Tory MPs “would be better employed looking to ensuring the health and safety of their constituents rather than posturing in order to ape England”.
A paper from the Welsh Government’s Technical Advisory Cell, which provides scientific advice to ministers, said allowing outdoor contact with members of other households “would have no more than a very small impact on overall transmission rates”.
It said it could “probably be safely allowed before contact tracing is in place”.
‘Latest scientific advice’
A Welsh Government spokeswoman said: “We review the coronavirus regulations every 21 days as required by law.
“This review is based on a range of factors, including the latest scientific and medical advice from our expert advisers; how the virus is behaving in Wales and compliance with the regulations. The Technical Advisory Cell provides scientific advice about the impact any changes to restrictions is likely to have on the transmission rate and this is published weekly.
“The clear and strong view of both the Scientific Advisory Group for Emergencies and the World Health Organisation is that governments should introduce changes one step at a time; the impact of these changes should be monitored and, if we are able to continue to slow the spread of the virus, we will introduce further changes at the next review date.
“Our approach to any easing of the restrictions will continue to be cautious and we will put people’s health and wellbeing at the forefront.”