The A New England hitmaker and folk star Turner are teaming up for a sold-out concert in aid of the Shelter charity on Wednesday (18Dec13) and they will preview the event on Tuesday (17Dec13).
They will travel to London's Kings Cross district to busk for an hour at lunchtime.
Bragg says, "The work that Shelter does is essential every day of the year, but never more so than at Christmas time. I am privileged to have the opportunity to join forces with Frank Turner in helping highlight and support the crucial work that they do."
Turner adds, "I've done a fair bit of work with Shelter over the years and I think what they do is fantastic and important; a society as affluent as ours could and should be able to make sure everyone has a stable roof over their heads. Bring Billy into the equation and it's a great way to sign off for the year and get ready for Christmas."
The exact location of the pair's busking session will be revealed on Twitter.com on Monday (16Dec13).