Prologis has gone public with a £12.6B ($16.6B) takeover bid for Segro after the UK logistics landlord rejected a deal that would rank among the largest real estate acquisitions in European history.

The world's biggest logistics REIT revealed that it had approached Segro on 16 June with an all-share proposal valuing the FTSE 100 company at 925p per share, a 24.6% premium to Segro's closing share price on Tuesday and an equity valuation of roughly £12.6B.

The offer values Segro at roughly its reported net asset value.

Under the proposed terms, Segro shareholders would own approximately 10.5% of the combined company. Prologis, which has a market capitalisation of about $141B, said the transaction would create a stronger global logistics platform with greater access to capital and enhanced development capabilities.

However, Segro's board has swiftly and unanimously rejected the proposal, describing it as opportunistic and significantly undervaluing the company.

"The board of SEGRO has unanimously and unequivocally rejected the proposal, which falls a long way short of SEGRO's own views on value," the company said in a statement.

Segro said the bid seeks to exploit a widening valuation gap between UK and European property companies and their U.S.-listed peers, a disparity that has widened amid geopolitical uncertainty and weaker sentiment toward European property stocks.

"The proposal was opportunistically timed and sought to take advantage of the clear dislocation between SEGRO's current share price and its highly attractive underlying business and strong prospects," Segro said.

The approach underscores the vulnerability of UK-listed property companies trading at steep discounts to underlying asset values.

Prologis said Segro's European portfolio is highly complementary to its own global logistics network and would strengthen its position across key urban distribution markets. Prologis also cited Segro's growing data centre platform as a key attraction and source of future growth.

Prologis argued that Segro has struggled under what it called "structural constraints," including a persistent discount to net asset value and a more leveraged balance sheet. Segro has traded at an average discount to its NAV of 17% over the past three years, Prologis said.

The U.S. giant said its stronger access to public and private capital would allow it to accelerate development projects and unlock value from Segro's land bank, power infrastructure and emerging data centre platform.

However, Segro pushed back strongly against suggestions that it needs a larger partner to realise that value.

The company said it has "a clear strategy, supported by a strong balance sheet and a proven operating platform," adding that momentum is building across its occupier markets. It also highlighted its "large and attractive development pipeline, including an exceptional data centre platform," and said it remains confident in its ability to generate substantial value independently.

Prologis has urged Segro shareholders to pressure the board into discussions, arguing that the proposal offers immediate value while providing exposure to future growth through ownership in the combined business.

Segro shares surged more than 19% after the disclosure. Under UK takeover rules, Prologis now has until 22 July to either announce a firm intention to make an offer or walk away.