Boris Johnson was unable to explain what single parents living in different counties should do if their child’s area is subject to tighter coronavirus restrictions than their own.

The prime minister was asked by Christopher, a single parent from Margate, Kent, what he should do about seeing his son, who lives in Essex, if his area is at a higher Covid alert level than his son’s - or vice versa.

Mr Johnson appeared to be unsure about the rules and told the Downing Street press conference on Friday that the father should look up the guidance online.

“Christopher I think the guidance, alas, is that - you should go on the website obviously and check - but when places go into a higher tier from the basic medium then there are restrictions on household contact, alas,” he said.

“So depending on how you define your household you may find there are restrictions.

“But you really need to go onto the website to see where, what’s going on in Kent and what’s going on in Essex in order to be absolutely sure.”

Although there are restrictions on households mixing in Tier 2 and Tier 3 of the local lockdown system, the prime minister failed to note that there are clearly defined exemptions from those rules for childcare reasons.

Government guidance states that households can form a “childcare bubble” for children aged 13 years old or under.

The following people are allowed to provide childcare support in private homes and gardens: registered childcare providers (including nannies), people in a household’s support bubble, or people in a household’s childcare bubble.

Like support bubbles, a childcare bubble must be between the same two households - they must also only be used for childcare and not be used as an excuse for households to mix in ways they would otherwise not be allowed to.

When Matt Hancock, the health secretary, announced the introduction of such bubbles in September, he said it was “essential that our children or dependents are well looked after and loved”.

A government spokesperson also told HuffPost UK this week that people were allowed to form childcare and individual support bubbles across tiers so a parent in a Tier 2 area would be able to travel to look after a child in a Tier 3 area.

However, the spokesperson added that people would be “encouraged to form these [bubbles] close to their home.”