The Rolling Stones have joined the campaign to increase revenues from streaming to musicians in the U.K., adding their names to a letter to the Prime Minister that has so far received only a noncommittal response.

The Stones join Tom Jones, the Bee Gees’ Barry Gibb, Emeli Sandé, the estate of the late Joe Strummer, Alison Goldfrapp and Jarvis Cocker of Pulp as new signatories.

The letter, which was sent in April, asks Boris Johnson to update U.K. copyright law so artists, performers and songwriters receive the same rights they have in radio, known as "equitable remuneration." So far, the letter has received an “interested but noncommittal reply,” according to NME.

The demand is a big ask with little chance of being fulfilled, but insiders hope the campaign will result in some movement in a situation many deem highly unfair, as revealed in evidence sessions for the recent government inquiry into the economics of streaming.

More than 150 artists have signed the open letter, including previously announced signees Paul McCartney, Bob Geldof, Annie Lennox, Lily Allen, Chris Martin and Kate Bush.