(ShareCast News) - Katherine Garrett-Cox has stepped down as chief executive Alliance Trust as part of a broader board shakeup after a battle with shareholder activist fund Elliott Advisors, the company said on Thursday. Garrett-Cox will step down from the board of Alliance Trust but continue as chief executive and a director of its fund management arm Alliance Trust Investments (ATI). Chief finance officer Alan Trotter is also quitting his job at the FTSE 250 firm. The current main board will be reorganised to be made up of non-executive directors, while a second board will be established for ATI, which will include independent non-executive directors.The changes come after US hedge fund Elliott argued that Alliance Trust's performance has been poor and had campaigned for changes to the board. The parties reached a truce in April when the company agreed to appoint two of the three candidates Elliott had put forward for positions on the board.The new board structure has been set up to "ensure necessary separation of shareholder and investment manager interests", the company said."This revised governance structure provides the board with greater clarity and flexibility in managing these two investments," the company said.Alliance Trust chair Karin Forseke said many shareholders indicated that they sought change."We have carefully considered the feedback we received and this is reflected in this announcement. They will provide our shareholders with an investment trust which aims to outperform a clear benchmark from a cost base which is among the lowest in the sector," she said.Alliance said it would now focus on global equities and dispose of non-core investments. It added that ATI would be awarded an investment mandate of 35bps on average net asset value, which it claimed to be "one of the lowest in the industry".It was also to use the MSCI All Country World Index (MSCI ACWI) as a formal benchmark, setting a clear measure against which to assess the Trust's performance.Cost reduction targets were also set, with an ongoing charges ratio of 45bps or less by the end of 2016 (against 60bps in 2014) and savings of £6m for 2016.The changes we be implemented by the beginning of March 2016, Alliance said.