The letter accuses Sir Paul Scott-Lee of failing to act on intelligence about the theft of charitable donations and suggests he should admit he cannot police the area adequately. It also asks for his resignation as chief constable.
The letter outlines how the details of one vehicle and its drivers have been reported to West Midlands Police on at least eight occasions for alleged theft of donations. Clothes Aid, which collects for Great Ormond Street Hospital Children's Charity, claims that the vehicle's occupants stole at least 12 tonnes of donations in about 90 days.
"We have consistently found the response to this crime from West Midlands Police very challenging," said Michael Lomotey, head of collection protection at Clothes Aid.
"Whereas most other police forces in the UK are looking at the problem of charity bag theft to some degree, West Midlands Police appear not to be concerned."
Metropolitan Police commanders at Territorial Policing Headquarters have agreed to consider Clothes Aid's action plans and new operational tactics.
A spokesman for West Midlands Police said: "We can confirm we are liaising with Clothes Aid to address some issues raised with them and that the liaison is ongoing."
Charity clothing collections are a lucrative fundraising activity, bringing in £550m a year in the UK. But bogus collections are on the increase and now cost genuine charities an estimated £3m a year, according to Clothes Aid (Third Sector, 5 September).