As his controversial 20-year reign at the helm of the Guggenheim Museum comes to a close, outgoing director Thomas Krens finds himself at the center of a new controversy, the Independent reports.

According to Basque investigators, Krens paid well-above-market rates to acquire works for the collection of the Guggenheim Museum Bilbao, whose launch at the end of the last century is generally considered his greatest achievement at the Guggenheim.

With a budget of €96 million ($122,088,695 in today’s terms) provided mostly by Basque regional authorities, Krens purchased works that caught his fancy, often from artists he knew and often paying more than the market demanded.

Javier Gonzalez de Durana, the Basque government's adviser to the museum between 1996 and 1998, has alleged that Krens built up the Bilbao museum's collection on the basis of "personal criteria and overpayments." Durana cited the acquisition of Large Blue Anthropometry by Yves Klein, explaining that the museum paid $2.7 million for the work, but that it was not worth more than $2 million.

Conservative Basque regional MP Arturo Aldecoa did not detail specific works, but he said that the collection was assembled “on the basis of visits by Krens to artists and exhibitions.”

The accusations emerged during investigations into a scandal that broke at the Bilbao museum in April over the embezzlement of €500,000 by the museum's former financial director and €6 million in poorly judged currency deals.

Richard Armstrong, former director of Pittsburgh's Carnegie Museum of Art, replaces Krens as director of the Guggenheim Foundation next month.