A Kuwaiti sheikh alleges that a senior executive at Switzerland's UBS offered $20m to get the bank an advisory role on one of the biggest-ever acquisitions in the Middle East, but the bank later backed out of the deal, according to the sheikh's testimony in a Dubai court case.

Sheikh Meshal Jarah Al Sabah said in sworn testimony that UBS offered the commission in 2009 to derail a bid by the French media group Vivendi for the African telecommunications assets of Zain, Kuwait's biggest mobile-phone company, and to get UBS a lead role finding a different buyer.