T-Online, Europe's largest internet service provider, is exploring plans to reinvent regional portals as gateways to selected online pornography websites as part of its efforts to boost revenue prospects.

Ya.com, bought by T-Online for €550m (£342m) last September, has signed an agreement with Nasdaq-listed pornography supplier Private Media Group to allow users access to its adult entertainment archives in a deal that could soon be extended to other T-Online portals.

T-Online, owned by Deutsche Telekom, hopes the introduction of pornographic content will bolster its share of subscription charges in the face of dwindling advertising orders. In March, T-Online was forced to write-off £203m from the combined value of its French portal Club Internet and Ya.com in Spain. "It is a fact that adult content is the most popular area of interest on the web," said Alvaro Ibanez, chief web officer at Ya.com.

"This co-operation [with Private Media] will provide our adult users with the best quality adult content, and, at the same time, it also guarantees security and privacy."

Last week, chairman Thomas Holtrop told a German newspaper: "You can make a lot of money with erotica. It is a lucrative business which we are examining very closely."

With Italian rival Tiscali threatening T-Online's position as Europe's largest ISP, Mr Holtrop said he planned to grow the German business by focusing on providing more lucrative content on its portals rather than buying up smaller competitors.