A man walks past London Stock Exchange in London, Britain.Photo:Xinhua

London Stock Exchange group (LSEG) announced Friday that the board rejected "the unsolicited, preliminary and highly conditional proposal from Hong Kong Exchanges and Clearing Limited (HKEX) to acquire the entire share capital of LSEG".

LSEG said in a statement that it was concerned about "the key aspects of the conditional proposal: strategy, deliverability, form of consideration and value".

In a letter to HKEX CEO Charles Li and Chairwoman Laura Cha, LSEG Chairman Don Robert said: "We are very surprised and disappointed that you decided to publish your unsolicited proposal within two days of receiving it."

"The (LSEG) board has fundamental concerns about your proposal," Robert said in the letter.

Meanwhile, LSEG said it continued to make a progress on its proposed acquisition of Refinitiv Holdings Ltd ("Refinitiv").

"Regulatory approval processes are under way and a circular is expected to be posted to LSEG shareholders in November 2019 to seek their approval of the transaction," said LSEG, adding that the transaction remains on track to close in the second half of 2020.

HKEX said on Wednesday it has made a proposal to combine the two companies. The proposed transaction values the LSEG at about 29.6 billion pounds (36.6 billion U.S. dollars), according to a statement by the HKEX.