THE Stock Exchange is demanding that Seapower companies and group head Francis Yuen make a public statement to clarify serious allegations made in documents leaked to the press on Tuesday. Head of listing Herbert Hui said last night: ''The allegations are of a serious nature and we take the matter extremely seriously.'' Should the allegations prove true they would represent the biggest scandal in Hong Kong since the conviction of former Stock Exchange chairman Ronald Li in October 1990. Mr Hui said last night the Exchange had received a copy of the documents, which were addressed to the chief executive, Paul Chow, along with a senior executive at the Securities and Futures Commission. ''We have sent a letter to Seapower asking them to give an answer to our inquiries. What we want is for them to consider putting out a public announcement as soon as possible to clarify the situation,'' said Mr Hui. He said the type of documents involved and the detail of information meant it was difficult not to take them seriously.