(Bloomberg) -- Direct Line Insurance Group Plc shares surged as much as 39% after the insurer rejected a £3.3 billion ($4.2 billion) takeover bid from Aviva Plc, the second suitor it’s rebuffed this year.

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London-listed Aviva submitted a non-binding proposal valuing Direct Line at about 250 pence per share, it said in a statement Wednesday that confirmed an earlier Bloomberg News report. The price represents a 58% premium to Direct Line’s Wednesday close.

Direct Line stock rose as high as 219.8 pence in early trading, below the value of Aviva’s offer. Aviva shares dropped as much as 3.6%.

“Aviva believes that an acquisition of Direct Line would deliver attractive returns for both Aviva and Direct Line shareholders, including unlocking value that is inaccessible to Direct Line standalone,” it said in the statement. “Aviva believes that the acquisition would deliver material cost and capital synergies, incremental to Direct Line’s existing cost savings program.”

Direct Line’s board rejected the proposal on Nov. 26, saying it substantially undervalues the company, and has declined to engage further with Aviva, according to the statement. Aviva is offering 112.5 pence in cash plus 0.282 new Aviva shares for each Direct Line share.

Direct Line said in its own statement on Wednesday that its board considered Aviva’s offer to be “highly opportunistic in nature.” It said that its board stands behind a newly-established leadership team and a strategy that it expects to “deliver attractive growth in profitability, capital generation and shareholder returns.”

Bloomberg News reported earlier Wednesday that Aviva has been speaking with advisers about a potential takeover of Direct Line. Shares of Direct Line have fallen 13% this year, giving the company a market capitalization of about £2.1 billion.

Under UK takeover rules, Aviva has until 5 p.m. local time on Dec. 25 to announce a firm intention to make an offer or walk away.

Aviva has started hunting for acquisitions again after Chief Executive Officer Amanda Blanc pursued a series of divestments that slimmed down the insurer and left it more focused on the UK. In March, Aviva said it was entering the Lloyd’s insurance market through a £242 million purchase of Probitas. Aviva shares have gained 13% this year, valuing it at £13.1 billion.

Last year, it agreed to buy Corebridge Financial Inc.’s UK protection business AIG Life Ltd. for £460 million. Aviva is among potential suitors that have been studying Esure Group Plc, the British home and motor insurance firm backed by Bain Capital, Bloomberg News reported last month.