The head of the New South Wales State Emergency Services (SES) has quit after being accused of misconduct.

Key points: Mark Smethurst was appointed SES Commissioner in February 2017

Mark Smethurst was appointed SES Commissioner in February 2017 His resignation was accepted today by Emergency Services Minister Troy Grant

His resignation was accepted today by Emergency Services Minister Troy Grant Mr Grant would not disclose the nature of the alleged misconduct

Minister for Emergency Services Troy Grant said he had accepted Commissioner Mark Smethurst's resignation this afternoon.

"I have no tolerance for misconduct and allegations will always be taken seriously, no matter who they relate to," he said in a statement.

"Appropriate measures have been put in place to support those affected by this matter."

Mr Grant did not detail the nature of the allegations.

It is understood the allegations were made only recently, and prompted an immediate investigation at which point the Commissioner was stood down.

Mr Smethurst was appointed Commissioner in February 2017, having served in the Australian Army for 35 years — most of which was spent in the Special Forces.

He was appointed a Member of the Order of Australia for services to operational planning in Iraq.

He was also awarded the Distinguished Service Cross for command and leadership in Afghanistan in 2006.

At the time of his appointment, Mr Grant described him as "a dynamic and practical leader".

Mr Grant said NSW Police Assistant Commissioner Kyle Stewart had been appointed interim SES Commissioner.

He said Assistant Commissioner Stewart — who runs the force's Communications and Security Command — had a "long and distinguished" career.

He joined NSW Police in 1985.