Labour has told Boris Johnson to “get off your backside” in responding to coronavirus, as cross-party support for the prime minister’s cautious strategy started to fade.

Opposition parties criticised the failure to properly explain why the UK is not imposing the wide-ranging restrictions implemented in other countries, at a “forceful” meeting to discuss emergency legislation.

Jonathan Ashworth, Labour’s shadow health secretary, demanded the government publish the scientific data said to justify the reason for keeping offices, schools and sporting events open for now.

Concern was also raised over the failure to take further steps to protect the elderly and most vulnerable – including possibly urging them to stay at home and out of contact with others.

John McDonnell also accused the prime minister of having “self-isolated himself” from coordinated international action to prevent a recession, in stark contrast to the response to the 2008 financial crash.

“There has been no leadership and no action from either the prime minister or the chancellor,” the shadow chancellor said. “It seems No 10 is following Donald Trump’s lead yet again.

“We are saying to Boris Johnson, bluntly, get off your backside and show some international leadership. That is what UK prime ministers of all political colours have traditionally done.”

Plaid Cymru, which attended the meeting, said: “You can see growing public concern and the government needs to be clear on the reasons why it is taking less action than other countries to manage the spread of Covid-19.”

Eyebrows were raised when the government sent Helen Wheatley, the little-known junior prevention minister, to the talks with the opposition parties.

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In contrast, Jeremy Corbyn, Ian Blackford and Ed Davey – leaders of Labour, the Scottish National Party in Westminster and the Liberal Democrats respectively – attended.

The criticism came as No 10 declined to echo the chief scientific adviser’s statement that it would be “helpful” for 60 per cent of the population to catch coronavirus in order to develop “herd immunity”.

However, the prime minister’s spokesperson did say the scientists advising ministers had been “very transparent” in setting out how the government expected the outbreak to develop.

Mr Ashworth said ministers should move onto the “explain stage” and explain “why their strategy is correct and the strategy in Ireland or Spain is incorrect”.

“If the government can publish more of the science, if they can publish the modelling they are basing their decisions on, if they can explain the assumptions and judgements they are making about human behaviour and allow scientists, other experts in the field, to stress test it, to peer review it, I think that will help maintain public confidence,” he said.

The Department for Health and Social Care is expected, later on Friday, to release specific advice for care homes, as some started to impose their own restrictions.