Posting comments that could be seen as damaging to a company's reputation could cost a third of all employed bloggers their jobs, according to a new report.

Human resources firm Croner said that companies could decide to charge employees with gross misconduct for making harmful comments or revealing sensitive data, which can be punishable by instant dismissal. 

Of the 2,000 bloggers surveyed by Croner, 39 per cent admitted to making comments that could be considered harmful.

"If there is a negative impact on the organisation's corporate image which is so serious that it breaches the implied term of mutual trust and confidence, the employee could be dismissed for gross misconduct," said Gillian Dowling, technical consultant at Croner.

"The blog could also be evidence of other conduct issues or reveal workplace discrimination or bullying."

Croner compared the situation to the emergence of unrestricted email during the 1990s, and said that staff often did not think about their responsibilities because it is so easy to post their opinions online.

The study was conducted for Croner by YouGov.