A survey of 1,000 companies using their LinkedIn profiles found that 0.24 per cent of people in medium-sized firms, and 0.019 per cent in large companies, worked in internal comms.
The report from the Institute of Internal Communication (IoIC) and comms consultancy Theblueballroom calculates that this leaves the figure for the total number working in internal comms at 45,760.
IoIC chief executive Steve Doswell said: "These figures confirm that internal communication has really come of age as a profession, with a significant number of individuals across the UK now firmly identified with the discipline. It's encouraging to see how organisations are recognising the value of internal communications to their bottom line.
"We know the numbers involved are small compared with sectors such as HR or marketing, but it is clear that we now have a sizeable profession and it is important this is operating to best effect. The institute believes these findings reinforce the need for high standards, sound governance and professional development to ensure the quality and competence of an internal communications workforce that is so important to consistent business success."
Sheila Parry, managing director of theblueballroom, said: "We've known for years that people are looking after internal communications from many different functions and at different levels, and so they haven't been easy to quantify. The IoIC decided that it wanted to address this and so our agency came up with a way to do it.
"We hope this opens some debate not only about how many internal communications practitioners there are but about how much impact they can have in their organisations. And we always want to know more - so that the IoIC can serve the needs of the sector and of their employers."