Robots have already begun taking the place of workers in a host of industries but how long before they replace politicians?

That was the thorny philosophical question French Prime Minister encountered during a visit to Japan on Monday. During one of his many meet-and-greets, Manuel Valls was introduced to Nao and Pepper, two chatty robots who deferentially welcomed him to the stage as "the minister of ministers".

"I very much admire the scope of their talent," Valls quipped in return. "But I hope in any case, for the moment, that their innovation stops before they are able to become a Prime Minister, or minister of ministers," he added. Valls' three day trip, which included a meeting with Prime Minister Shinzo Abe on Saturday, has been billed as a celebration of Japanese-French cooperation. Pepper and Nao are both good examples of that. They were designed and programmed by French robotics company Aldebaran before it was purchased by Japanese mobile giant Softbank. Both robots are available for purchase in Japan with Pepper - which, according to its makers, can read people's emotions - costing a cool $1,600.

The steep price tag has done little to dent its popularity in a country obsessed with robots.

Within a minute of Pepper going on sale in June, the initial shipment of 1,000 units sold out. But Softbank do not want their technological marvel becoming too popular with users.