The initiative is called "Come Back Leon" after a 1980s TV advert where tasty pasta lures youngsters away as their elders plead: "We have the same at home!"

Aimed at the high-flyers who were children then but left in despair at red tape and poor prospects, the adapted catchphrase "We are innovating at home!" carries the message not that they were wrong to leave, but that it is time to return.

Despite France's reputation as a high tax, low growth, bureaucratic country, the claim to be a centre for dynamic young companies has some foundation.

It was the most represented nation for a fourth successive year in the Deloitte 2014 top 500 index of Europe's fastest growing tech firms, counting 86 companies in total. Paris also claims status as the startup capital of Europe.

A tax structure that encourages research and development spending provides another ingredient, along with a strong research bent in the country's universities.

The Come Back Leon scheme has a modest budget of "several hundreds of thousands of euros" (dollars) according to Frederic Mazzella, the founder of successful car-sharing website BlaBla Car. It is funded by the members themselves and by the state's La French Tech initiative.

The project members reckon the startup sector will need to fill 3,000 jobs this year alone. But entrepreneurs at Wednesday's launch know they have their work cut out winning over cynical expats who have found their niche elsewhere.

"Every time we look to recruit someone for a big post, we ask the question can we go looking in the United States or another country, and each time the recruitment firms tell us 'no, they'll never come back'," said Bertrand Jelensperger, founder of lafourchette, created in 2006 and now a 400-million-euro a year online restaurant booking firm that is part of U.S.-based TripAdvisor.

"That's frustrating."

The group believes it has plenty to aim at - estimating that 2 million French people live abroad, about half of whom have the degree level-plus profiles they are looking for.

The 40,000 or so working in Silicon Valley are a primary target, and the group is planning roadshows in New York, San Francisco and London this summer.

(Reporting by Andrew Callus; Editing by Katharine Houreld)

By Andrew Callus