The Military Wives' single has become the fastest seller for six years and could hit the half-million mark by the end of the week, virtually guaranteeing it will be Christmas number one.
Gareth Malone's choir sold more in two days than X Factor winners Little Mix sold last week following their victory in the TV talent contest.
The Wives shifted 242,000 copies of their track Wherever You Are up to last night, figures showed today.
The Official Charts Company said the sales tally is the biggest since Shayne Ward's That's My Goal in 2005, which sold 313,000.
Little Mix were thought to be their only real challenger for the Christmas number one, and so far the Wives are outselling the girl group by a margin of six to one.
The choir was put together by Malone for a BBC Two series, which climaxed with the group performing at the Festival of Remembrance at the Royal Albert Hall.
The Military Wives were giving their single, which was championed by Radio 2's Chris Evans, an even greater push today by launching it with a performance at HMV in Oxford Street.
DJ Evans arrived in a military Jeep to hand out mince pies to the wives after they performed for shoppers outside the central London store.
He said his listeners gave him no choice but to play the single, adding: "They watched the show and loved it and loved the record."
Malone said the song had caught the public imagination because it had been released at "a particular moment". He said: "This single has come at a time when we're thinking about Afghanistan, we've been there 10 years and the feeling for the armed services is really positive in the country at the moment."