BERLIN - German President Christian Wulff, an ally of Chancellor Angela Merkel, said he did use the villas of business friends for private holidays, the latest twist in a scandal that could cost him his job after just 18 months.

Although the president's role is largely ceremonial, damaging headlines reflect badly on Merkel as she pushed for his appointment.

Under pressure from the media, Wulff said in a statement through his lawyers that he had spent six holidays in villas belonging to entrepreneurs while he was serving as premier of Lower Saxony from 2003 to 2010.

The statement added that "these holidays...had no relation to his public offices" and "this behaviour is entirely compliant with the rules of the Lower Saxony law".

Wulff, 52, drew negative headlines in January 2010 after spending some of his Christmas holidays in the US holiday home of his entrepreneur friend Egon Geerkens because he had accepted a free upgrade to business class for the flight.

And he came under further fire last week over accusations he misled regional lawmakers about a 500,000-euro loan which he obtained on special terms from Geerkens' wife.

Wulff denied the accusation, although he expressed regret for failing to mention the loan in a parliamentary hearing, when questioned about his business relations with Geerkens.

As media furore over his behaviour has escalated and new accusations have emerged, some lawmakers from both the opposition and the coalition have called upon him to step down.

The front page of Spiegel magazine sported a photo of Wulff with the headline "The Wrong President" at the weekend, while mass-selling Bild am Sonntag blared "Wulff wobbles" in bold characters.

Wulff has been an uncontroversial figure up until now after Merkel pushed for him to take over from former IMF chief Horst Koehler.