The director and executive director of the National Theatre have announced their exit dates from the charity having previously advised that it was time to give way to new blood after each spending more than a decade in their roles.

Director Nicholas Hytner will step down at the end of March 2015, while executive director Nick Starr will leave in 2014, both will have spent 12 years at the Theatre by the time they stand down.

Chairman John Makinson rung praise for the duo upon their announcement yesterday: "Nick Hytner and Nick Starr have led the National Theatre to undreamt levels of creative and commercial success over the past decade. Today’s announcement will not come as a surprise, as we have known for some time that they planned to initiate a phased succession process in the course of 2013. It is a sad moment for the National Theatre nonetheless," he said.

The charity's income has increased by 65 per cent between 2007 and 2012, not least due to the incredible success of the company's War Horse production in the UK and internationally. War Horse pulled in £18m in 2012, 22 per cent of the charity's £80.5m overall income, although also accounting for 20 per cent of its £73.5m expenditure. In that period the Theatre's separate box office income also increased from £15.4m to £20m. And the charity reduced its reliance on its Arts Council England grant, which remained steady at £18.3m, from 38 per cent of its income to 23 per cent of its income. 

Despite the London-based Theatre's success, Hytner used his foreword in the charity's latest accounts to impress upon its readers the importance of funding for the arts regionally and his nervousness over its continuation: "There is a pressing need to recognise that special support must be given to cultural institutions in the regions," he said. "They face a double threat – from cuts to their Arts Council funding and to local government funding. If theatres are required to play safe, they quickly lose an audience with a taste for adventure, to the point where they play safer still and eventually risk losing any audience whatsoever.

"It would be a tragedy if a generation of creative artists outside London was denied the modest assistance it needs to maintain a lively dialogue with its audience. So there are pressing cases for support for the arts in London, and outside of London. And there is no need for the two to be in competition with each other. They are interdependent. After nine years at the helm of this great theatre, I am at the same time as apprehensive as I have ever been about the future, and as excited as I have ever been by what I see around me," he said.

The board of the charity will advertise for the new director next week with an appointment expected to be announced in autumn. The executive director will be appointed once the director designate is in place. The National Theatre's current executive team of four includes Lisa Burger as chief operating officer and Kate Horton as deputy executive director in addition to Hytner and Starr.

Hytner said yesterday: "It’s been a joy and a privilege to lead the National Theatre for ten years and I’m looking forward to the next two. I have the most exciting and most fulfilling job in the English-speaking theatre; and after twelve years it will be time to give someone else a turn to enjoy the company of my stupendous colleagues, who together make the National what it is."

The National Theatre, situated on London's South Bank, was registered as a charity in 1963 and has over 1,000 employees. It is supported by a number of trusts and foundations.