The DEC, the coalition of 13 charities that launches appeals in response to humanitarian crises, said that seven million Yemenis did not know where their next meal was coming from and children were dying from malnutrition.
It said 20 months of war in Yemen had brought the country "to breaking point".
A DEC statement said: "DEC member charities are reaching millions of people across the country with life-saving aid, such as food and treatment for malnutrition, but much more needs to be done to help those in dire need."
Tearfund, one of the members of the DEC, said on its website that more than 18.8 million people – more than three-quarters of the country’s population – were in urgent need of humanitarian assistance.
The DEC said the government would provide match-funding for public donations made to the appeal up to a total value of £5m.
The charity said seven member organisations were already responding to the crisis and three more were planning to support the response through in-country partners.
Advertisements for the appeal fronted by the actor Tom Hardy and the presenter Clare Balding will be run on all major UK broadcasters from today.
Saleh Saeed, chief executive, of the DEC, said: "Now is the time to save lives in Yemen before it is too late. Children face the greatest risk of starvation – almost half a million infants and young children need immediate treatment for malnutrition.
"DEC members are already providing treatment for malnutrition, running mobile health teams, distributing emergency food and cash but they need funds to reach more people."
A donation line and website opened yesterday.