The Association of British Insurers slammed mining group Xstrata's plans to reimburse key managers' big retention packages to ensure sustainability after its proposed merger with rival Glencore.

The influential shareholder body condemned the decision of the underwriter and was quoted by Reuters as saying, "The ABI is always skeptical about the effectiveness of retention payments."

"In this case we have raised further concerns around the significant retention awards being offered to Xstrata executives which are not linked in any way to performance."

The watch dog issued a rare "red-top" alert on Xstrata’s pay plans.

Xstrata has prepared a talent retention strategy, under which it has provided nearly $267.56m to its top 73 executives based on the expectation that their expertise would be beneficial for the future growth of the firm.

Standard Life Investments and Fidelity, Xstrata’s investors, have previously declared their opposition against the miner’s pay plans.