Plimsoll Publishing, which has reported on the state of the PR sector for the past six years, says the gap between the winners and losers this year is markedly greater than before.
David Pattison, a Plimsoll senior analyst, said: 'The industry is growing at six per cent on average, but there's a band of 70 companies growing at about 50 per cent a year and about a quarter companies losing 20 per cent a year.'
Among the 70 companies growing fastest, the report says 31 could be putting themselves in financial risk in pursuit of new business.
'It does not mean the business is an overall success just because it is seeing growth - maybe they are borrowing more money or taking less margin. There is evidence that companies are putting themselves at risk,' said Pattison.
The report looks at the most recent accounts of 1,000 companies and predicts that more than one third will not see growth at all this year.
Less than half of these companies were making efforts to reduce their asset base, the report warns.
The highest market-share earners listed in the report include Joe Public Relations (up 120 per cent), Fleishman-Hillard UK (up 126 per cent) and Gnash Communications (up 95 per cent). Some of these gains are the result of mergers within holding groups.