Lululemon has accused founder Chip Wilson of holding “outdated perspectives” as the activewear giant ramps up its defence in an increasingly bitter proxy fight.

The yoga wear retailer said it had unsuccessfully attempted to settle the dispute with Wilson last week, delaying the filing of its definitive proxy statement in the hope of reaching an agreement.

Wilson, who founded Lululemon in 1998 and owns 8.6 per cent of the business, has been pushing to install three directors on the company’s board after publicly criticising the retailer’s leadership and warning that the brand has lost its “cool” factor.

In a regulatory filing made on Monday, Lululemon issued its most detailed public rebuttal since the dispute began late last year, claiming Wilson’s views on how the business should position itself are no longer fit for the brand’s future.

The retailer said Wilson’s actions had been “damaging to the brand” and were harming “the very stakeholders he claims to represent”.

“Electing any of Mr Wilson’s nominees would endorse his misguided perspectives,” the company said in a letter to shareholders.

Lululemon said Wilson had recently countered its proposed settlement terms with a plan that represented “a significant departure” from previous discussions. According to the filing, he sought the immediate appointment of two of his nominees, with a third director to be chosen from a pool he selected.

He also asked for quarterly meetings with Lululemon’s incoming chief executive and several directors.

Wilson pushed back hours later, insisting the dispute could be resolved quickly and that he remained willing to be constructive. He said he believed the two sides were moving towards a settlement and claimed directors had not made clear where the current disagreements stood.

“The notion that I want to dictate strategy to Lululemon is just wrong,” Wilson said, adding that he stood by his nominees and believed their brand and marketing expertise could benefit the business.

The row comes during a turbulent period for Lululemon, whose shares have fallen 62 per cent over the past 12 months amid design missteps, slowing momentum and mounting concerns over its brand appeal.

The company, which has a market value of around $14bn, has also been losing ground to fast-growing rivals including Alo Yoga and Vuori.

Lululemon recently named former Nike executive Heidi O’Neill as chief executive, following the exit of Calvin McDonald earlier this year. However, shares fell on the news of her appointment, despite some investors praising her industry experience.

It also added two new directors in recent months as it looks to revive growth and stem market share losses.

Lululemon has urged shareholders to back its three directors up for election, including former Levi Strauss chief executive Chip Bergh, describing them as “vastly superior” to Wilson’s nominees.

Investors are expected to vote next month, unless the two sides reach a settlement before then.

Wilson is not the only investor to have pressed for change at the retailer. Activist investor Elliott Investment Management built a stake worth more than $1bn last year and had previously urged the board to appoint former Ralph Lauren executive Jane Nielsen as chief executive.

Elliott has not publicly commented on Lululemon’s decision to appoint O’Neill.

Click here to sign up to Retail Gazette‘s free daily email newsletter