The Government is being urged to improve diversity in the Civil Service after a report found under-representation of women, ethnic minority staff and people with disabilities.

The National Audit Office (NAO) said there had been improvements in levels of representation of all three, but this had slowed recently, and there remained "issues" at senior level.

Around 53% of civil servants are women, but at senior level the figure is 38%, while six out of 17 departmental heads are female, the report found.

Minority ethnic representation in the Civil Service increased from 4% in 1988 to 10% last year - 2% below the figure for the total working population - falling to 7% in the senior Civil Service.

Representation of people with disabilities remained low at 5%, the spending watchdog said.

The study also reported that the Cabinet Office had found that some people were leaving the Civil Service because they found the culture "exclusive".

Amyas Morse, head of the NAO, said: "The Civil Service needs a workforce that reflects our increasingly diverse society and to embrace an inclusive approach, for both strategic and operational reasons.

"This is especially so at a time of ongoing austerity when the service will have to do more with less.

"Up to now, the Civil Service has concentrated upon a central approach to improving the representation of groups with protected characteristics.

"We consider that building on the progress that has been made will also depend in future on greater emphasis by individual departments upon an 'inclusive' approach to managing their civil servants, encompassing all characteristics and all staff.

"Such an approach, rather than solely focusing on levels of representation, is more likely to result in a productive and engaged workforce and the business benefits needed."

Public and Commercial Services union general secretary Mark Serwotka said: "The Civil Service must do more to ensure its top ranks reflect society and staffing in departments, including improving training and development and ditching its appraisal system that we believe is discriminatory.

"We have consistently raised these issues with the Cabinet Office and it is very disappointing it wasted the opportunity to utilise our expertise when developing the latest version of the talent action plan."

An Equality and Human Rights Commission spokesman said: "If our Civil Service is to continue to be regarded as a world leader, it needs to draw on all talents across our communities.

"The slow progress in improving diversity suggests there is a lot more to be done.

"The Civil Service needs to urgently tackle these issues with new vigour and intensity.

"Today's report reveals a serious under-representation of disabled people, ethnic minority staff and women at senior levels of the Civil Service.

"Unless more action is taken, it risks failing to draw on the full potential of the communities it seeks to serve."

A Cabinet Office spokesman said: "We have a world-class Civil Service which is much more diverse than in the past and more diverse than the majority of British employers, but we know there is lots more work to do.

"We must become more representative of those we serve in order to truly govern for one nation and open up even more opportunities for people from all backgrounds to progress.

"We now have a diversity champion in every department who will hold our feet to the fire and help implement our talent action plan."