Since it was set up in 1997, TLC Lottery has raised more than £1.6m for its three founding charities - Acorns Children's Hospice, Birmingham St Mary's Hospice and Birmingham Focus on Blindness. They established the lottery after all three were turned down for National Lottery grants.
TLC Lottery manager Colin Barrett said that, with 15,000 weekly players, the scheme was a "phenomenal success" and it now wants to invite other causes on board.
Charities can be nominated by players or contact the lottery directly for an application form. The scheme is free to join, and applications will be considered by the three owner charities.
At least 45p from each £1 ticket goes to TLC's founding charities. But once new charities join, buyers can elect to divert another 45p to one of them. The remaining 10p pays for administration and the weekly cash prize, which is currently £2,000.
Seventeen more organisations have joined the lottery since 1 May, including hospitals and hospices, medical research charities and schools and sports teams.