Jim Lawless descended to 101m in the No Limits category, which involves descent by weighted sled and ascent by balloon.
His dive was carried out off Sharm El Sheikh in Egypt, with support by Only One Apnea Centre and with AIDA judges present.
It beat the 77m UK men's record set by Paul Whincup in 2005. No British women's record has been set in the category.
The world No Limits records are held by Austrian Herbert Nitsch at 214m and Tanya Streeter at 160m.
The British Freediving Association has said that it is “looking forward to more [British] 100m-plus dives in the next year or so” – and not necessarily in No Limits.
It said that “with our Constant Weight records for men and women now both in the 90s, it may not be long before someone does it without a sled”.
Sara Campbell holds the UK and world women's record at 96m, and Dave King the UK men's record at 91m.
The Constant Weight men's world record is held by Nitsch, at 124m.
Related links
British Freediving Association
AIDA (world governing body)