Edinburgh-based Standard Life Investments, a major shareholder in Royal Dutch Shell, said on Friday it would vote against Shell’s $50 billion bid to buy BG Group.

David Cumming, head of equities at Standard Life Investments, said the investment firm concluded that the proposed terms of the acquisition of BG are “value destructive” for Shell shareholders.

“This view is based on the downside risks to Shell’s oil price assumptions plus the tax and operational risks surrounding BG’s Brazilian asset base,” said Cumming. “Consequently we shall vote against the deal.”

The BG deal would make Shell the world’s largest liquefied natural gas producer. It is already Europe’s largest oil company.

Guy Jubb, head of governance and stewardship at Standard Life Investments, said the upcoming shareholder meetings to approve the deal would be a test of investor stewardship and the “responsible use of shareholder rights.”

“We have a clear responsibility to vote our shares in the best interests of our clients,” said Jubb.

“We have engaged with Shell to explain our views and to encourage them to re-negotiate.

“By voting against in respect of our clients who have an interest in Shell we are sending a clear message to Shell’s board, reinforcing our opposition to the deal on the proposed terms.”

Standard Life Investments holds 0.4% of the A shares in Royal Dutch Shell and 1.7 % of the B shares, making it the company’s 11th-biggest shareholder. According to Bloomberg, Standard Life Investments is also the 16th biggest shareholder in BG with a 1.3 percent stake.

Shareholder advisory firm Institutional Shareholder Services (ISS) has supported the Shell-BG deal.