German brothels are offering customers the chance to sleep with as many prostitutes as they like for a single fee, in recession-busting deals criticised as immoral by politicians.

The "flat-rate sex" promotions, which are based on all-you-can-eat restaurants, have been introduced by brothel owners in a bid to revive trade that has fallen around 30 per cent in the economic downturn.

Other imaginative offers include rebates for pensioners and people on benefits, 10 per cent discounts for men who arrive by bicycle or public transport, and free shoe-polishing for customers who stay overnight.

But it is the flat-rate deals – which are priced as low as £60 (€70) – that have attracted particular controversy in a country where prostitution is legal and generally well-tolerated.

The promotion is popular [with] brothel owners who have to pay their sex workers a fixed daily wage whether or not they have any clients...