Cofunds has passed £10bn in assets, five years since it launched.
Rival FundsNetwork is also understood to have reached the £10bn landmark.
Industry estimates put the amount of money held on platforms at around £30bn but Cofunds believes this will leap to £180bn by 2010.
Cofunds is to launch an offshore bond and will include offshore funds on the platform next year. This year, it has added a single-premium bond and personal pension following its tie-up with Legal & General. Expansion and development has come at a price, with Cofunds posting reported losses of £200m since launch in 2001.
Chief executive Charlie Eppinger says: “We only opened for business in 2001 so this is a terrific achievement. We have seen a number of competitors trying to break into this market but few have succeeded in achieving scale. We will only continue to grow at our current pace if we continue to invest in the business.”