Gerhard Schroeder has seen his ratings suffer in the polls

Lothar Vosseler, 57, Mr Schroeder's younger half-brother, will appear on the reality show for a day.

He will go into the Big Brother house on 13 June to coincide with the European Elections.

The German version of Big Brother, which is now into its third series, regularly invites celebrities into the house to spice the show up.

The latest series - which lasts for 12 months - began on 1 March with the contestants vying for a prize of 1m euros (�700,000).

Secret police

Mr Vosseler's appearance in the reality show is unlikely to please his real-life big brother, who has seen his popularity decline in Germany after a series of economic reforms.

And it is not the first time the chancellor has had to fend off potentially embarrassing publicity from members of his family.

In 2002, Mr Schroeder's sister, Ilse Bruecke, attacked her brother's withdrawal of tax benefits for single parents like herself.

And in 2001, it was revealed that one of Mr Schroeder's cousins worked for the former East German secret police.

'Political debate'

Mr Vosseler, who has struggled to hold down a job, said: "The station wants my visit to provoke political debate. As brother of the chancellor, I'm ideally suited."

He added: "I'll have a good look round, that can't harm. Then I'll decide when to go out. Maybe I'll stay a week."

Chancellor Schroeder's father died during World War II and Mr Vosseler was born after his mother married a second time.