Michael Gove said he “expected” the Prime Minister to announce it himself on Monday.
Mr Johnson is believed to be planning to give a press conference at 5 p.m. from Downing Street, confirming England can enter Stage 3 on the roadmap.
This will allow people to meet indoors for the first time since the New Year, in groups of up to six people and two households.
Pubs, restaurants and other holiday accommodation will probably be able to reopen indoors under these conditions, with groups of no more than 30 people allowed outdoors.
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Travel abroad will be allowed for the first time – but only to a small list of ‘green list’ countries, while others require quarantine on return.
Mr Johnson will also give an update on hugging between family and friends – where reports claim he could say hugging will be allowed in ‘common sense’ situations for the first time since March 2020.
Meanwhile, the limit of 30 mourners at funerals is expected to be lifted from May 17, ahead of schedule. Weddings will still be limited to 30 guests.
Social distancing rules more generally, including in pubs and restaurants, will remain in effect until at least June 21, the fourth stage of the roadmap.
Cabinet Minister Mr Gove told Sky News: “Thanks to the success of the UK vaccination program, as well as the common sense of citizens across the UK, we can gradually ease the measures.
“So I anticipate that tomorrow the Prime Minister will signal that we can enter the next stage of detente in England on May 17th.
“And to add the transport secretary said yesterday, this also means that some of the rules on international travel are also changing.”
As part of the February lockdown roadmap, May 17 was a major unlocking point for the company.
Outdoors, most social contact rules should be lifted – in other words, the two-household limit or the rule of six. But gatherings of more than 30 people outside will remain illegal.
Indoor mixing will again be allowed – but subject to restrictions.
Indoors, gatherings will be limited to the rule of 6 or a larger group of no more than 2 households, whichever is greater.
This means that people will be able to take family breaks in England with up to five friends, or more as long as there are only two households in total.
It also means that you are allowed to spend the night with friends and family elsewhere in the country for the first time.
The interior of pubs and restaurants also opens at this point – but only table service remains.
Entertainment such as cinemas and theaters, children’s play areas, remaining accommodation (hotels, hostels and guesthouses) as well as adult sports groups and exercise classes are also open.
If you meet friends inside the pub, it’s the 6 or 2 household rule, whichever is greater. But those restrictions are removed if you are in the beer garden, and there is only the limit for gatherings of 30 people left.
Performances and sporting events will also undergo changes in Stage 3. Larger indoor events with a capacity of 1000 or half full (whichever is smaller) will be permitted.
Outside, a capacity of 4000 people will be authorized, or half full, always depending on the smaller of the two.
In larger open-air venues such as larger football stadiums, up to 10,000 people will be able to attend – or a quarter full, whichever is lower. So 10,000 can go to Wembley Stadium.