The application of Zurich's smoking ban has weakened progressively since its implementation exactly two years ago, according to media reports.

Many bars and restaurants have relaxed the rules on smoking indoors, online new site 20 Minuten reported.

“Officially, we are of course a non-smoking bar - unofficially we apply the smoking ban only until midnight,” a bar worker from Zurich told the website.

To avoid problems if the police call around for a spot check, the bar never puts out ashtrays. Cigarette butts on the floor do not prove that the bar tolerates the practice, the worker said.

An employee of another bar told the website that they ask smokers simply not to smoke at the windows or where they can be seen.

“It is worrying that the smoking ban is not enforced consistently," the president of the Lung Association Zurich, Alexander Turk, told 20 Minuten.

“It is extremely important that the legislation is adhered to - otherwise it degenerates into a farce," he said.

Last year Switzerland saw restaurant and bar revenues fall by approximately 2 billion francs ($2.2 billion). The losses were partially blamed on the introduction of the smoking ban, news website Basler Zeitung reported.