A Scottish animal welfare charity today accused its English counterpart of "stealing food from the mouths" of Scotland's animals.
The Scottish SPCA launched a scathing attack on the RSPCA, accusing it of fundraising north of the border, despite not operating there.
Scottish SPCA chief executive Stuart Earley said research showed 70% of the public wrongly believed the RSPCA saves animals in Scotland.
And he said this was having a major impact on the amount of money raised by his own charity for animal welfare work.
But the RSPCA insisted that donors contacting its offices are directed to the Scottish charity and denied deliberately advertising in Scotland.
The Scottish SPCA today launched a campaign urging the RSPCA - which only covers England and Wales - to make it clear in its publicity that it does not operate in Scotland.
Mr Earley said: "Many people do not know that the RSPCA does not rescue or re-home any animals in Scotland and by advertising here it has been intentionally adding to the confusion to make money.
"The RSPCA is in breach of Institute of Fundraising guidelines it helped draw up, which require charities to be explicitly clear about where they work.
"Occasionally using small print to tell the Scottish public it is registered in England and Wales is in no way explicit.
"We are a completely separate charity and have asked the RSPCA to make it clear it does not save animals in Scotland so people can make an informed choice about who to donate to. However, after six months of talks we are no further forward.
"This has been increasing the huge pressure on our resources for many years and enough is enough. It's time the RSPCA told the truth."
Mr Earley also accused the RSPCA of launching a campaign to target supermarket customers in Scotland.
He added: "Further RSPCA advertising has included television adverts on UK channels.
"While these particular adverts cannot be restricted to England and Wales, they should not deceive the Scottish public."
Mr Early suggested the RSPCA should alter its name to reflect its geography.
The Scottish SPCA said it enjoys a stronger position because animal welfare is devolved to Holyrood.
A spokeswoman for the RSPCA said: "We are extremely surprised by this, given that the RSPCA and Scottish SPCA regularly work together on a range of issues to help animals.
"The British public, whether in Scotland, England, Wales or Northern Ireland, expects charities to collaborate and co-operate, and during these difficult economic times it makes even less sense for charities to attack each other. The RSPCA will be doing whatever we can to resolve this dispute.
"The RSPCA does not deliberately advertise in Scotland and goes to great lengths to ensure wherever possible that our adverts are not distributed outside of England and Wales.
"We always make every effort to exclude advertising messages reaching Scottish consumers, and Scottish donors who contact us via RSPCA fundraising campaigns are directed to the Scottish SPCA."