Paper and box maker Smurfit Kappa has rejected a takeover approach from a rival company which it called "unsolicited and highly opportunistic".
Shares in the company were up 18.4 per cent at 3,010p in early trading.
US-based International Paper made a proposal to acquire the company, with shareholders receiving a combination of cash and a minority stake in the enlarged company.
Read more: Smurfit Kappa joins FTSE 100
But Smurfit Kappa's board said today that it has decided it is in its best interest to "pursue its future as an independent company".
"The proposal fails entirely to reflect the group's strong growth prospects and attractive industry outlook," the statement said.
Smurfit Kapp is Europe's largest producer of paper packaging and last year its earnings before interest, tax depreciation amortisation exceeded €1.2m (£1.07m).
Liam O’Mahony, Chairman of Smurfit Kappa said “The board of Smurfit Kappa has unanimously rejected this unsolicited and highly opportunistic proposal. It does not reflect the group’s true intrinsic business worth or its prospects.
"We delivered a record performance in 2017 and underlying trading momentum has continued into 2018. The group has a proven management team which we believe will deliver significantly greater value for shareholders on a stand-alone basis."
It said it had made the announcement without the consent of International Paper.