Staff exodus and cash crisis at the Tate

Tate Modern is simultaneously facing a financial crisis and an exodus of senior staff.

The gallery's director of programmes, Sandy Nairne, has admitted that financially Tate Modern is " operating at an unacceptable level of risk".

Mr Nairne's comment comes as it emerged that the Tate's director of collections Jeremy Lewison has become the latest of Tate supremo Sir Nicholas Serota's senior staff to quit, as he starts a freelance curatorial career after 18 years with the Tate.

Louisa Buck, editor of the academic journal The Art Newspaper, believes Mr Lewison's departure - the third high-level defection from the Tate in two years - may be connected to Sir Nicholas's directorial style.

"Perhaps some of the trouble lies at the very top," she said: "While no one doubts the achievements of Sir Nicholas in the masterminding and delivery of Tate Modern, as well as his adept handling of the relaunch and rebranding of Tate as a cultural monolith, there are many rumbles that his powers of delegation often leave a great deal to be desired."

Sir Nicholas is recruiting a new director for Tate Modern after Lars Nittve quit the post in his first year to run the Moderna Museet in his home country, Sweden.

Another defector from Sir Nicholas's regime is Iwona Blazwick, the former head of exhibitions and display, who quit to direct the Whitechapel Gallery.

The Tate's difficulties come in advance of a new round of government funding for major national galleries which is widely expected to stay at current levels.

When the wow wears off