More than a billion pounds is likely to be added to the stock market valuation of retailer Kingfisher with the flotation of the first French internet service provider on the Paris Bourse later this month.

The Libertysurf ISP - modelled on the UK's Freeserve, which was developed by Dixons - was backed by Kingfisher and French tycoon Bernard Arnault's private investment company when it was created last year. The two backers each poured 50m euros (£30m) into the venture, taking 45% stakes. Less than 12 months later they are sitting on stakes valued at only a little less than £1bn each.

France's bourse regulator confirmed yesterday that shares in Libertysurf would be priced at 35.5 to 41 euros each, valuing the ISP at 3.05bn to 3.52bn euros.

Libertysurf is raising 518m euros by selling 12.6m new shares but the two main backers are not reducing their holdings. They will be left with 40% stakes.

Shares in Kingfisher, which owns the Woolworth, B&Q, Comet and Superdrug chains plus a network of European retailers, climbed 35p or 6.9% to 545p as details of the float were disclosed.

Analysts say the flotation is bound to be oversubscribed and believe Libertysurf will increase the scale of the offer. "It is the first offering to give a pure French internet play," said an official from Deutsche Bank France, the issue's lead manager.