The London Stock Exchange has turned down a 950p per share cash bid from New York's Nasdaq exchange.
The LSE said in a statement that the offer, which is subject to conditions, 'substantially undervalues' the company. The bid values the LSE at about £2.4 billion.
The move comes just weeks after the LSE saw off a £2.16 billion bid by Australian bank Macquarie.
The LSE said the Nasdaq offer represented only an 8% premium to the current market price. The exchange also referred to its 'extremely strong' growth prospects, citing record levels of trading in the first two months of this year.