* Chairman Haste says will take more active role
* Search for new permanent CEO is ongoing (Adds comment from Wonga chairman)
LONDON, Nov 20 (Reuters) - Britain's biggest payday lender Wonga said on Thursday that acting chief executive Tim Weller stepped down last month, becoming the third person to leave the job in the past twelve months.
Chairman Andy Haste, a former chief executive of RSA Insurance Group, who joined Wonga in July, said he would take a more hands on role to push through changes at the lender, which has come under fire for its treatment of customers, while the search for a permanent CEO continues.
"I'm taking a more active role in leading the business. This was a mutual decision, following a comprehensive handover, and will ensure clear leadership in the weeks and months ahead," Haste said in a statement.
Wonga has seen several senior executives depart over the past year, including co-founder Errol Damelin. The business has come under intense scrutiny from lawmakers and regulators, who have attacked its sky-high interest rates. Wonga's website lists its representative annual interest rate as 5,853 percent.
Britain's financial regulator said last week it would cap the interest short-term lenders -- or so-called payday lenders -- can charge.
Such lenders offer to tide borrowers over until they receive their salary, and anti-poverty campaigners say the sector has grown sharply in recent years as the cost of living rises and some people struggle to access credit.
Wonga's previous chief executive Niall Wass stepped down in May, just six months after replacing Damelin, and Weller was appointed as interim chief executive at that time. (Reporting by Matt Scuffham; Editing by Steve Slater and Mark Potter)