"An investigation was launched in August 2011 by officers from the Economic and Specialist Crime Command following allegations by West Ham and the Olympic Park Legacy Company in respect of the unlawful obtaining of information," a Metropolitan Police statement said on Tuesday.
"A 29-year-old man was arrested in connection with the investigation. He was arrested at an address in Sussex on suspicion of fraud offences and has been taken into custody at a Sussex police station, where he remains."
Speaking to the London Assembly, she said: "My board were put under surveillance by Tottenham Hotspur and the chairman of Tottenham Hotspur felt confident enough to say that in the Sunday Times several months ago, that all 14 members of my board were put under surveillance.
"The Metropolitan Police are now conducting an investigation into that surveillance. There has been all kinds of behaviour here that I could not have anticipated which, believe me, has not been pleasant in the last 12 months."
"The club did not undertake, or instruct or engage any party to conduct surveillance on any member of the OPLC committee whatsoever and we consider the making of this baseless accusation to be wholly inappropriate and irresponsible," a club statement said.
"We totally reject this accusation in the strongest possible terms."
