The London Stock Exchange Group (LSE) has rebuffed the £ 31.6 billion bid from its Hong Long rival in a blistering rejection that branded the approach "fundamentally flawed".
The LSE said its unanimously rejects the proposed takeover from Hong Kong Exchanges and Clearing (HKEX) and said it was "no merit" in holding talks with the suitor.
Aside from flaws in the proposal, the LSE also said the £ 83.61 a share price "if substantially short".
The LSE said: "The board has fundamental concerns about the key aspects of the conditional proposal: strategy, deliverability, form of consideration and value.
"Accordingly, the board unanimously rejects the conditional proposal and, given its fundamental flaws, sees no merit in further engagement."
Shares in the LSE lifted 3%.
Its withering put-down comes after HKEX launches its surprise cash-and-shares takeover bid on Wednesday in a move set to disrupt the LSE's planned 27 billion US dollars (£ 21.9 billion) deal to buy data provider refinance.
While shares first surged on Wednesday's shock announcement, they soon got back.
HKEX said the proposal was dependent on the refinance of tie-up being scrapped.
Don Robert said the board was "surprised and disappointed".
He went on to say that his deal with Refinitive has "strategic logic" and has so far been received by investors.
"In stark contrast, the high geographic concentration and heavy exposure to market transaction volumes in your business would represent a significant backward step for LSE strategically," he added.
The LSE also has concerns about the HKEX's relationship with the Hong Kong government – which is the largest shareholder in the exchange, with a 6% stake.
HKEX shares, which are the "inherited uncertain", especially given the unrest and protests in Hong Kong.
HKEX is the best route into that, preferring to renegotiate its existing partnership with the Shanghai Stock Exchange.
Mr Robert concluded: "LSEG, especially when compared to the significant value we expect to create," is not applicable Refinitiv. "
Neil Wilson, chief market analyst at Markets.com, said it was "no great surprise to see the LSE board has politely but firmly rejected the HKEX bid".
He said: "Unattractive, offering a puny dowry and coming with volatile and unpredictable parents, HKEX never looked like the ideal bride."
"The question now comes in a counter offer."