Labour's obsession with league tables is damaging children's education, a damning international report has found.

Headteachers are overloaded with bureaucracy and their intense competition for high rankings is having a 'negative' effect on many pupils.

Some schools are suffering worsening results as poor league table rankings send them into a 'vicious' downward spiral.

Pressure: Pupils at at King Edward VI High School answer questions during an English lesson. The drive for schools to do well in league tables could be creating a 'negative' atmosphere for many

The preliminary findings from the Organisation for Economic Co-Operation and Development are a blow to the Government. They come shortly after the Commons' schools select committee warned that 'teaching to the test' is endemic.

The report looks at school leadership in 22 of the 30 developed nations that make up the OECD. It says that schools in England strive for a good reputation in order to attract 'gifted and high-achieving pupils'.

The ranking by exam results is therefore 'extremely important to establish and protect'.

But the report notes the consequences of these league table rankings 'are often negative' for both the school and its pupils.

While the tables favour schools that are already advantaged, less successful schools have to battle against a 'vicious circle'.

This includes, a 'bad reputation, worsening atmosphere, decreasing identification of the pupils with their school, decreasing number of pupils, reduction of resources, decreasing job satisfaction and motivation among staff, lack of applications of well-qualified teachers, worse quality of lessons, decreasing pupil achievement and worse results in the league tables'.

The report adds: 'Different studies show that most headteachers disapproved of the great competitive pressure open enrolment and league tables had produced.'

The report, due to be published shortly and leaked to the Times Educational Supplement, also looks at the Government's drive to improve standards by increasingly introducing initiatives.

It claims the number of schemes introduced in the last couple of years is 'unusually extensive compared to other countries worldwide'.

The OECD states that the 'sheer number of initiatives and programmes and the speed at which schools are expected to implement them may be counterproductive'.

'True improvement results from a balance of making best use of innovative ideas and concepts on the one hand and maintaining proven ones on the other,' the report says.

' Focus should be on making improvements to the current framework on the basis of experience and feedback.

'Care should be taken to limit new initiatives that increase the overload and fragmentation experienced by school leaders and communities.'

The Department for Children, Schools and Families yesterday defended league tables.

'It is right parents have the information available as just one factor in deciding which school is right for their child, and right that pupils are able to measure themselves against a national standard,' a spokesman said.

Last week, the Commons' schools select committee said the system of tests, targets and league tables 'may actually be contributing to the problems of some children'.

'We believe that the system is now out of balance in the sense that the drive to meet Government-set targets has too often become the goal rather than the means to the end of providing the best possible education for all children,' MPs said.

Meanwhile, a deputy head is quitting marking Key Stage Two papers for 11-year-olds due to the incompetence of ETS Europe, the not-for-profit company that is running national test marking for the first time this year.

Tony Bate, of Ysgol Maelgwn primary school in Conwy, Gwynedd, said the last straw was a garbled email from the company that was littered with spelling mistakes.