A statement issued by the transport specialist said there was ‘no question of any impropriety in our work'.
It also accused the newspaper of confusing fundamental parts of its business and ‘misrepresenting legitimate aspects of our work'.
The broadsheet's front-page splash last week - headlined ‘Labour's lobby scandal' - detailed the experiences of an undercover reporter who infiltrated Golden Arrow for eight weeks.
The newspaper claims to have a recording of Golden Arrow consultant Ivan Henderson, in which he allegedly says that prisons minister Gerry Sutcliffe had offered him access to his diary.
Henderson - a former Labour MP - is also reported to have described his professional dealings with transport minister Stephen Ladyman as ‘a bit dodgy sometimes'.
One public affairs industry source told PRWeek: ‘It looks like he has been name-dropping to impress a young employee, but he doesn't seem to have done anything wrong.' No one at PA trade body APPC was willing to comment on the issue.
Golden Arrow is in talks with lawyers over its next move. It confirmed Henderson is still a full-time staffer. The joint founder of Golden Arrow is Andrew Sharp.