The head of MI5 has said he is concerned over new lines of communication between terrorists, particularly internet phone calls.

In an interview with The Daily Telegraph yesterday, spy chief Jonathan Evans expressed concern that such calls represented a "significant detriment to national security" and that new powers were needed to tackle the threat.

"If we are to maintain our capability we are going to have to make decisions [on powers to intercept communications] in the next few years," he said. " Because traditional ways are unlikely to work."

The government is expected to publish a consultation paper on a communications database of emails and internet communications in the next two months, after the original plans to introduce legislation for such a database were postponed last October.

It emerged last month that there is a proposal in the consultation for such a database to be run by a private sector company.

But the measures have come in for criticism from Sir Ken Macdonald, the former director of public prosecutions.

"The tendency of the state to seek ever more powers of surveillance over its citizens may be driven by protective zeal," he told The Guardian. "We must avoid surrendering our freedom as autonomous human beings to such an ugly future."

The Information Commissioner has also said that such a database would be a "step too far".