Officials have introduced new measures that ban people in England from socialising indoors with anyone not already in their household bubble.
Up until Monday, the person visiting another's house would have been the one in breach of lockdown rules.
But now both people could be prosecuted under the new amendment to The Health Protection (Coronavirus, Restrictions) Regulations 2020 bill.
Previous rules simply stated people should "stay at home" and avoid all but essential travel, forgoing wording about meeting in private places.
But the amendment to the bill now makes clear only those with "reasonable excuses" will be allowed to meet indoors, with sex not featuring on the list of exemptions.
"No person may, without reasonable excuse, stay overnight at any place other than the place where they are living," it says.
Those who may be deemed to have a reason for meeting others indoors are sports professionals, people attending funerals, vulnerable persons fleeing a risk of violence, carers and those with unavoidable work commitments.
