PARIS, July 28 (Reuters) - French luxury group Kering is bulking up its fashion portfolio with the purchase of a 30% stake in Valentino but that will do little to reduce its dependence on weakening top brand Gucci, at least in the short term.

After stellar growth between 2015 and 2019, Gucci - which accounts for half of Kering's sales and almost two-thirds of its operating profit - has lagged rivals LVMH and Hermes , struggling to keep pace with their post-pandemic rebound.

Kering last week announced a major management reshuffle, including the exit of Gucci veteran CEO Marco Bizzarri, in a bid to revive sales at the brand. The group appointed managing director Jean-Francois Palus as interim Gucci CEO as it seeks a permanent replacement.

On Thursday, as the group posted lower-than-expected revenues for the second quarter, it also unveiled a surprise 1.7 billion euros ($1.9 billion) investment in Valentino, famous for its haute-couture and red-carpet designs.

Kering, is buying 30% of the Italian brand from Qatari investment fund Mayhoola and has an option to buy the rest in the next five years. The group also said it wanted to broaden its strategic partnership with Mayhoola, and that could lead to the fund taking a stake in Kering.

The M&A buzz failed to lift Kering shares on Friday, with the stock down 2.3% at 0824 GMT.

The stake in Valentino, which had 1.4 billion euros in sales in 2022 compared with Gucci's 10.5 billion euros, is "nice but long-term," said Exane-BNP Paribas analyst Antoine Belge.

"It is neither too small or too big, it is quite profitable but with room for improvement. However, Kering only taking a minority share means it does not move the needle short-term, notably in terms of lowering Kering's dependence on Gucci."

Centerview advised Kering on the deal, while Valentino said Rothschild and Intesa Sanpaolo advised Mayhoola.

($1 = 0.9119 euros) (Reporting by Silvia Aloisi and Mimosa Spencer in Paris, and Elisa Anzolin in Milan Editing by Mark Potter)