Boris Johnson and Jeremy Corbyn have both paid tribute to NHS staff and other public sector workers in their Christmas messages.
Mr Johnson used his first festive message as prime minister to thank those staff working over the holiday.
He also expressed "solidarity" with Christians around the world who face persecution for their beliefs.
Labour's Mr Corbyn said it was a time of year when "the scale of injustice and inequality" is in "plain sight".
He praised people working in food banks and emergency shelters over Christmas.
Scotland's First Minister Nicola Sturgeon also thanked volunteers and those working in the public sector over the festive period.
In his message, the PM wished the public "a merry little Christmas" and thanked those working in the NHS, the police and other public services as well as military personnel on deployment with the armed forces.
Mr Johnson, who will be spending his first Christmas as PM in Downing Street with his partner Carrie Symonds, said the government "stands with" Christians around the world who are facing persecution for their beliefs.
"For them, Christmas Day will be marked in private, in secret, perhaps even in a prison cell," he said.
"As prime minister, that's something I want to change.
"We stand with Christians everywhere, in solidarity, and will defend your right to practice your faith.
"So as a country let us reflect on the year, and celebrate the good that is to come."
In his sign off, he urged the public to enjoy the festive period, joking: "Try not to have too many arguments with the in-laws - or anyone else."
Mr Johnson and his partner are due to see in the New Year on the private Caribbean island of Mustique, the BBC understands.
In what is likely to be his last Christmas message as Labour leader, Mr Corbyn reflected on his general election defeat, while expressing his hope for a "better world".
He said: "This has been a difficult year for many of us.
"We didn't succeed in delivering the change that so many people so desperately need," he said.
"But Christmas is a chance to listen, reflect and remember all the things that bind us together: our compassion, our determination to tackle injustice and our hope for a better world."
Mr Corbyn praised those working in food banks and emergency shelters, helping the less fortunate.
"While we celebrate being together, we are reminded of the many who will be alone and sadly lonely at Christmas," he said.
"But our communities are built on generosity and the solidarity that comes from that.
"So we do not walk by on the other side."
Mr Corbyn has previously said he will stand down as leader "early next year".
The race to replace him has already begun, with shadow foreign secretary Emily Thornberry the first MP to officially throw her hat in the ring.
In her Christmas address, Ms Sturgeon praised those who give up their time to help others and urged people to "spread some Christmas cheer" by volunteering or "by being a good neighbour or friend".
The SNP leader called for Scots to be "especially thankful" for those working in the public sector over the Christmas period.
"For many Christmas isn't a holiday at all - for example, for the people in our NHS and indeed all of our public services," she said.
"Your efforts are appreciated all through the year. But they are particularly appreciated at Christmas time."
In his message, acting Liberal Democrat leader Sir Ed Davey spoke about his Christian faith and the "hope, joy and love" of Christmas.
He said: "What could possibly represent hope, joy and love better - than a newborn baby.
"When I held my first child, in the crook of my arm in Kingston Hospital, just minutes after he'd been born, that was the first time I really understood how my own father and mother must have loved me.
"So you don't actually have to believe in Jesus to recognise that for Christians, Christmas has a deep, profound meaning."