Gulf Keystone Petrol has attacked a former director in the latest round of its bitter battle with M&G Investments.The oil and gas company said Jeremy Asher, one of M&G's four proposed new board members, was a "disruptive presence" when he was a director before 2010. Gulf Keystone also said Asher was not independent enough because he holds 1.7% of the company's shares.In a letter to shareholders, Chairman Simon Murray and Lord Guthrie, who heads the nominations committee, said none of M&G's candidates had enough experience in any industry to be directors of a FTSE 250 company or the knowledge and abilities to oversee an oil and gas company.M&G, which owns 5.1% of the company, is unhappy about governance issues including a lack of independent directors, pay and conditions and the appointment of Murray, the former chairman of Glencore.Gulf Keystone met M&G on July 12th after interviewing three of the fund manager's candidates: Philip Dimmock, John Bell and Thomas Shull."Following the meeting, the board unanimously recommends shareholders to vote against all of the proposed M&G candidates," Gulf Keystone said in a statement to the Stock Exchange.Gulf Keystone said it had interviewed its own three highly qualified potential directors and would update shareholders when appointments were made.