Goldman Sachs Group Inc. has switched sides to advise Aviva Plc on its £3.3 billion ($4.2 billion) takeover bid for Direct Line Insurance Group Plc, only eight months after helping the target successfully defend against another suitor.

Direct Line Insurance Group said it rejected the 3.28 billion pounds ($4.16 billion) takeover approach from insurer and asset manager Aviva as it substantially undervalued the company. Describing the approach as highly opportunistic,

Direct Line’s shares surged as investor’s hoped the rejection might pave the way for a second takeover bid from the U.K.’s largest insurance company

The insurance giant, led by Amanda Blanc (pictured), revealed last night that it tabled an offer for its smaller competitor worth 250p a share.

Aviva has contacted shareholders in Direct Line Group (DLG) to convince them to reconsider its takeover offer. That was according to the Financial Times (FT), which said that the move “could pave the way for a hostile takeover bid for its smaller rival”.

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.

Direct Line topped gains on the FTSE 250 mid-cap index, while Aviva's shares fell around 3 per cent to be the top percentage loser on the blue-chip FTSE 100 index.

(Reuters) -Shares in UK's Direct Line Insurance soared over 36% in early trade on Thursday after it rejected a 3.28 billion pound ($4.16 billion) takeover offer from bigger rival Aviva, saying it "substantially undervalued" the company.