BERLIN (Reuters) -Lufthansa's management should be more vigorous in fending off resistance from labour representatives, top investor Klaus-Michael Kuehne was quoted as saying on Saturday, pointing to the airline group's share price.

Lufthansa is counting on lucrative transatlantic routes as it strives to revive its namesake core airline, bogged down by wage talks and high pay, and find new sources of revenue as it struggles to compete with Asian carriers.

Shares in the group, which includes brands like Swiss, Austrian and more recently Italy's ITA, have gained around 6% year-to-date, roughly in line with its peer Air France-KLM but lagging well behind British Airways parent IAG.

Kuehne told the Welt am Sonntag weekly newspaper that the German group had structural problems, adding that resistance from the works council and walkouts made management's work difficult.

"Whether the executive board takes sufficient action remains to be seen. In my opinion, more could be done," said the 87-year-old billionaire investor, whose company Kuehne Aviation is Lufthansa's biggest shareholder with around a 15% stake.

He also owns stakes in Swiss logistics group Kuehne + Nagel and German chemicals trader Brenntag.