Steve McComish told PRWeek that at least one tech blog had been duped after a fraudster using the name Sarah Baker used the company's logo and branding in an email.
The emails said that London PR wanted to pay to place hyperlinks in the blog.
After these links were put into the site, the editor contacted McComish to chase payment. McComish confirmed that Baker did not work for the agency and that the request had not come from London PR.
"Our logo must have simply been downloaded from the site and I'm angered that someone has been using our brand for this purpose," he told PRWeek.
"We have worked hard for the past nine years to build our business and then someone thinks they can hijack it like this."
McComish said that fraudulent activity like this could easily go unnoticed, especially when it was for smaller amounts, and urged PR firms to double check all invoices.
The issue has been referred to lawyers but it is unclear if any action can be taken to track down the anonymous fraudster.