People should be “extremely careful” about who they mix with in the run-up to Christmas if they are planning to see elderly relatives over the festive period, the Health Secretary has warned.

Matt Hancock said people should take “personal responsibility” around what they choose to do before and within the five-day period during which restrictions are relaxed.

He was asked at Monday’s Downing Street briefing if people should self-isolate from now if they want to see elderly loved ones next week.

He said: “I think that if you want to see elderly relatives at Christmas, we all know that the best thing to do is to make sure that you don’t have coronavirus, and the best thing you can do if you want to see elderly relatives at Christmas is to be extremely careful now about who you see.”

He said it is important that people are careful in this period “two weeks ahead, making sure you minimise the chance of both catching the disease and passing it on”.

He warned the public that it is not about “doing the maximum that the rules allow, it’s about taking personal responsibility”.

The UK Government and devolved administrations have agreed a joint plan to relax rules between December 23 and 27.

England’s chief medical officer Chris Whitty also struck a cautious tone, saying people should not meet at Christmas just because they can.

He told the No 10 press conference: “The point of this (relaxation of rules) is for, under certain circumstances, families who wish to, to get together, but they really have to be very, very careful.

“And in particular, incredibly careful if they’re around people who are vulnerable, who are at very high risk of this virus.”

He said the vaccine will “give us a way out”, but that will not happen by Christmas or in the two months afterwards.

He said: “We need to be really conscious of the fact that only by protecting one another, and particularly protecting the vulnerable over this period, are we going to get through to the point where people have been properly protected, and we can return to having the kinds of relationships with family that all of us want.”

He said there is a “really difficult balance between doing things that are the least damaging we can achieve, whilst keeping the virus under control – walking that really narrow path”.

Other experts have warned that relaxing restrictions throughout the UK over Christmas will have consequences.

Dr David Nabarro, a World Health Organisation (WHO) special envoy working on Covid-19, said the price of such a relaxation “could well be very high”.

Urging people to think carefully about their plans, he told Times Radio: “Just ask yourself, is there any way in which you can perhaps not have the family get-togethers this year?

“It’s much better not to do it when there’s this kind of virus about.”

Linda Bauld, professor of public health at the University of Edinburgh, said she was concerned about people travelling from areas with high infections to parts of the country with lower prevalence of the virus.

But she added that if the Government reneged on the relaxation pledge then trust in politicians could be eroded further.

Professor Stephen Reicher, of the University of St Andrews, said: “Right now we are heading towards disaster.

“Given high levels of infection across the country and the increasing levels in some areas (such as London) it is inevitable that if we all do choose to meet up over Christmas then we will pay the price in the new year.”

Independent Sage is calling for a pandemic fuel allowance so people can keep their homes ventilated while turning up the heating to stay warm.