The Dutch gambling authority has written to a number of online betting companies warning them to stop targeting the Netherlands in the run up to the World Cup and the Tour de France.

If they continue to do so, the firms risk fines and being excluded when licences are awarded for online betting in the future.

At the moment, online betting is banned in the Netherlands although changes in the law are expected to come into effect next year.

The gambling authority said it has contacted five to 10 major betting firms but declined to say which they were, Nos says.

The Dutch government currently has a monopoly on gambling.