The LSE has fought tooth and nail to keep away from the grip of the Nasdaq.
The competition authority said the two must ensure the independence of the LSE's clearing services, LCH.
The LSE is also said to be in talks with Euronext, Europe's Nasdaq-equivalent electronic exchange.
The LSE's chief executive, Carla Furse, had rejected the offer as undervaluing the exchange.
"What the LSE is saying we dispute, " he told BBC Radio 4's Broadcasting House programme.
The Canuck challenge to what it regards as the LSE's imperial ambitions may not succeed.
The London School of Economics (LSE) cited concerns about restrictions that "threatened academic freedom".
Roger Hardy is a visiting fellow at the Centre for International Studies at LSE.
LSE's business in British shares, but the exchange would be dotty to bet on this.
LSE's board made no comment on the new proposal, citing (understandably) the absence of a price.
LSE's board rejected as too low, but which pricked the interest of its institutional investors.
The LSE says crossly that the table does not capture excellence in social sciences.
LSE's horror if, after all the diplomatic dancing, some Internet upstart were to race past.
LSE's Mr Hills, the government ought to brush up the quality of its data.
"Today's announcement is a success for LSE shareholders, " said Peter Lenardos, analyst at RBC Capital Markets.
But a spokesman for the LSE told Reuters that trading would be as normal on Monday morning.
Both bidders were also warned not to obstruct access to the LSE's clearance provider by any competitor.
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The Grantham Institute at the LSE has released a briefing paper about the economics of wind power.
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LSE's efforts in Latin America and also highlights the extent to which London now dominates mining finance.
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We knew that LSE would be publicly identified if any LSE students were recognisable on Panorama (several were).
BBC: Panorama row: Six students on N Korea trip criticise LSE
"I'm also surprised that the LSE's consent wasn't sought, although this wasn't a formal LSE visit, " he said.
Opponents of the plan to buy LSE are thought to own at least half of Deutsche Boerse's shares.
BBC: Deutsche Boerse shareholders had opposed the LSE bid move
The LSE said that the BBC journalists had used a university society to set up the controversial trip.
Far more important, to them, would be the kind of long-term strategic choices highlighted in the LSE's report.
LSE's share-dealing owners created rules and trading systems which favoured themselves over their customers, investors would go elsewhere.
It was only in 2003, says Julian Le Grand of the LSE, that Mr Blair had his epiphany.
It's not hard to see two leagues forming--one linked with the NYSE, the other including the LSE and Nasdaq.
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There has even been speculation that Euronext and Deutsche Boerse could merge with each other, leaving the LSE isolated.
It was part of the LSE undergraduate program in that decade for example.
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Among LSE's other shareholders are Barclays PLC, with a 5% stake, and D.
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