FRANKFURT, August 6, 2008 (AFP) - The German radio and television broadcaster ProSiebenSat.1 posted on Wednesday a second-quarter sales increase of 45.4 percent owing to the acquisition of the Luxembourg media group SBS, but said it had suffered from the weak performance of free TV activities.

Consolidated sales gained 250 million euros (388 million dollars) to 801.9 million in the three month period, a statement said, while recurring core earnings rose by 28 percent to 203.7 million euros.

Business was nonetheless 'adversely affected in the second quarter by a lack of acceptance of the new German ad sales model,' the statement said.

ProSieben changed the way it sells advertising after it was hit last year by a regulatory fine of 120 million euros for illicit arrangements with competitors on the television advertising market.

In addition to losses linked to the new ad model, 'the European Soccer Championship also reduced ad bookings in the second quarter,' owing to matches broadcast by rival channels.

Proforma, or comparable, results for the group were also less positive, showing a 4.0 percent fall in sales and 16 percent drop in core earnings.

'The first half of the year was not an easy time for the ProSiebenSat.1 group,' the statement quoted chief executive Guillaume de Posch as saying.

'The reasons are clear: part of the market did not accept the German ad sales model,' which was revised in May.

'We will begin to regain market share in the second half,' he pledged.

Shares in the broadcaster fell by 2.26 percent to 6.05 euros in morning trades, while the MDax index on which they are listed had gained 0.87 percent overall.