Columbia Threadneedle Investments, one of the top five shareholders in the Restaurant Group, has said it will vote against the group’s proposed acquisition of rival restaurant chain Wagamama.

The investment firm opposed the £559m cash acquisition of Mabel Topco, the parent company of Wagamama, which according to its recent quarterly reports carries a ratio of 4.3x leverage to earnings before interest, tax, depreciation and amortisation.