Boris Johnson has promised the "maximum possible transparency" in sharing with the public his calculations over the easing of lockdown restrictions.

The Prime Minister said he was not in a position to say when or how the measures would be relaxed when he gave his first speech after three weeks off with coronavirus.

But, standing in Downing Street on Monday, he said the Government would be sharing more on this "in the coming days" as the nation entered its fifth week of lockdown.

Ministers have faced growing demands from Tory MPs, Labour leader Sir Keir Starmer and businesses on giving greater clarity on a way out of the severe restrictions.

Amid fears over how long the public can continue with the struggle to adhere to the measures, Mr Johnson warned that the fight against Covid-19 is now at the point of "maximum risk".

But he said the UK is "coming now to the end of the first phase of this conflict" as he prepares to refine the "economic and social restrictions" while ensuring the disease does not rapidly spread.

"We simply cannot spell out now how fast or slow or even when those changes will be made, though clearly the Government will be saying much more about this in the coming days," he said.

"And I want to serve notice now that these decisions will be taken with the maximum possible transparency.

"And I want to share all our working and our thinking, my thinking, with you, the British people."

He pledged to build "the biggest possible consensus" by "bringing in opposition parties as far as we possibly can".

Mr Johnson acknowledged the "R" value - the transmission rate of coronavirus - should be kept below one, meaning that on average anyone infected passes it on to fewer than one other person.

But he must decide how restrictions can be eased while maintaining this - perhaps by allowing certain sectors to resume their roles and allowing limited social interactions while ensuring effective testing.

So far, more than 20,000 people have died with the disease in hospitals, but the true death toll is likely to be far higher when care homes and other settings are accounted for.

Transparency over Mr Johnson's decision will allow the public to understand and abide by the changing rules, and give dormant businesses the ability to plan for a return to action.

One area where ministers have been facing intense calls for openness is over the membership of the Scientific Advisory Group for Emergencies (Sage), which is informing the Government's decisions.

It has emerged that Dominic Cummings, the PM's controversial adviser, has attended meetings of Sage, provoking opposition fears that political bias could taint the secretive group's advice.