One of IHG's largest shareholders has implored the hotel giant to reconsider offers made for the business.
In May it was reported that IHG turned down a £6b offer from an unnamed American suitor.
Now Marcato Capital Management, which owns 4% of IHG shares, has released a letter to fellow shareholders encouraging them to back their calls for a strategic review of the business.
It said: "Following media reports of a £6b unsolicited offer that was quickly rebuffed by the board of directors of IHG, we grew concerned that the board was not giving due consideration to the strategic alternatives available in the current industry and M&A environment. We hoped to engage in a constructive dialogue with the board and IHG's management regarding a process to explore potential options for enhancing long-term shareholder value."
The letter, signed by managing partner Richard McGuire, added the firm's suggestions had been dismissed by IHG.
"Ultimately, IHG's board has an ongoing duty to consider whether the company's current business plan is likely to create as much or more value than can be created through a combination with another major hotel operator," it added.
In response IHG said that it maintains an active dialogue with shareholders and welcomes feedback.
The statement said: "The board regularly considers all options for driving shareholder value. IHG met Marcato on 22 September 2014 and 29 October 2014 and reviewed its analysis. Following this review, the board has concluded that it remains in the best interests of all its shareholders to continue to pursue its current strategy for high quality growth and delivering strong operational and financial performance."