Angry customers of Australian web hosting company Melbourne IT are threatening to leave the company after a "migration" left their websites and email offline, in some cases for up to a week.

In an attempt to deal with the matter, managerial staff at the company, which is one of Australia's largest web hosting firms, have been "manning the phones" as ongoing issues around customer account migration, and a separate email delay issue, continue to overwhelm their customer support lines after weeks of problems.

Mea culpa: Melbourne IT chief executive Martin Mercer admitted the company did not have enough support staff.

Frustrated customers continued to publicly slam the company in comments on its Facebook page as late as Friday, with the comment thread dating back to December 17.

Some customers complained of waiting up to two hours or more to speak to someone at Melbourne IT's "24/7 Support" centre - only to have their call cut off.