The controversial 118800.co.uk mobile phone directory service has crashed, after thousands of users flocked online to remove their numbers from the site, according to reports.

The site, which launched last month, now displays a holding page which reads: "Service suspended while we make improvements."

The firm obtained up to 16 million mobile numbers from market research firms and online businesses that require customers to leave their contact details, according to The Daily Telegraph.

Although it does not hand out phone numbers to those who pay to use the service, it will connect a caller to the person they are looking for, leading some campaigners to complain that it is an invasion of privacy.

However, UK data protection watchdog the Information Commissioner's office (ICO) has given a green light to the service, which includes a simple ex-directory opt out on the web site. Connectivity, the company behind the service, said that it only bought customer information which was already in the public domain.

The Twittersphere has been awash with posts from angry users who are unable to get on the site to make themselves ex-directory, some calling for either Ofcom or the ICO to reappraise the fairness of the service.

The message currently displayed on the site says that it is undergoing major developments and will be "back as soon as possible with the new improved service ".

"All ex-directory requests made by people in our directory to date are being processed," it adds. "There will be no need to resend these requests. And we will take further ex-directory requests when the service resumes. We will not be taking ex-directory requests by phone or text whilst the service is not operational."