The London Stock Exchange (LSE) has denied reports that it has received an approach from its US counterpart.
The London Exchange has turned down a string of possible suitors
Shares in the exchange closed 18 pence lower at 1238p after it issued a statement denying an approach from the New York Stock Exchange (NYSE).
Rumours of an NYSE offer came two weeks after US rival Nasdaq paid £447.7m ($780m) to buy a 15% stake in the LSE.
Takeover speculation has swirled around the exchange for months, resulting in its shares almost trebling in value.
Experts had suggested that the Nasdaq's recent decision to buy a stake in the London market would put it in a better position than any prospective rivals should it decide to launch another bid for the LSE.
The LSE has already rebuffed approaches from the Nasdaq, Australian bank Macquarie and Germany's Deutsche Boerse.
However, it is believed that major shareholders in the LSE are now coming round to the idea of a takeover - for the right price.
Rumours that the NYSE was about to make an offer gained strength after last week amid unconfirmed reports that the US group was considering buying shares from certain LSE investors.
"In response to recent press speculation the London Stock Exchange would like to confirm that it has not received an approach from the New York Stock Exchange about a possible offer," the LSE said in a statement.
The statement comes a week after LSE investors overwhelmingly backed a £510m cash return to investors that was promised when the LSE fended off Macquarie's bid earlier this year.