NEW YORK - Private equity firm Blackstone Group Inc told Reuters on Tuesday it has made five additions to its environmental, social and governance (ESG) team, as its steps up the implementation of sustainability and diversity initiatives across its businesses.

The hirings come as buyout firms seek to burnish their ESG credentials. While their lucrative leveraged buyouts have won them a loyal investor base, more investors are now asking questions about their impact on jobs and the environment.

"We view ESG as central to our mission of delivering strong returns for clients," said Blackstone president Jonathan Gray in a statement.

Blackstone said Elizabeth Lewis, who previously worked on climate and impact investing at the International Finance Corporation, will help implement ESG policies across Blackstone's businesses.

James Mandel, who led a carbon-free building program at the non-profit group Rocky Mountain Institute, will lead Blackstone’s emissions reduction program.

Blackstone also appointed Caroline Hill and Nina James as heads of real estate ESG for Europe and Asia, respectively. Hill is joining from Lloyds Banking Group Plc, where she was head of responsible business. James was previously at Investa Property Group, one of Australia's largest commercial real estate companies.

Blackstone has also promoted Rita Mangalick to global head of ESG for its hedge fund and credit businesses, where she will work on reporting, policies and engaging with investors.

The New York-based firm is also in the midst of a search for a global head of ESG, people familiar with the matter said.

Blackstone rolled out a program last year to cut carbon emissions by 15% across new investments where the firm controls the energy usage. It plans to expand this to all its portfolio companies.

The private equity firm last year said it would aim to have diverse directors fill one-third of the seats on its portfolio companies' boards.

(Reporting by Jessica DiNapoli in New York Editing by Sonya Hepinstall) ((Jessica.DiNapoli@thomsonreuters.com; 646-223-4678;))