Nearly three-quarters of UK workplaces restrict their employees’ access to the internet, according to a recent survey by office design company Maris Interiors.

The survey found 74% of employers restrict internet access for staff in some way, with 71% of offices having a filter for pornographic websites.

More than half (52%) of employees are unable to access social networking sites such as Twitter or Facebook and 48% of employees are unable to access their personal email.

YouTube was blocked by 30% of employers and news websites by 27%. Just under a tenth (9%) of offices only allow access to certain specific sites and 4% only allow staff to use the company's intranet - not even allowing search engines such as Google.

Of those employees who have restricted internet access, 30% say this makes their job more difficult - and 82% say it makes their job more boring. Only 6% of employees surveyed said that they actually think it helps with their productivity at work.

Maris Interiors chairman Michael Howard said: "It is a difficult decision about blocking websites in the workplace - by doing so you have to balance employees' productivity against their morale. At our company, we restrict access to pornographic sites - hopefully, this doesn't affect their morale too much."

Maris Interiors polled 260 employees online between 7 and 11 March 2011.