The Labour party has warned that more has to be done to lever up the standards of those getting low grades or no grades. Peter Kilfoyle, a Labour education spokesman, said there was now a 12-fold gap between the top 20 per cent of GSCE results and the bottom 20 per cent.

According to Mr Kilfoyle, the gap emerges from an analysis of last year’s results. The conversion of GCSE grades to a points score shows that the average pupil in the bottom 20 per cent score five points, compared with 60 points for the average pupils in the top 20 per cents.

The proportion of 15-year-olds leaving without even a single grade G at GCSE has gone up from 7 to 8.1 per cent over the past two years. In two schools as many as half the year group leave without a qualification and in Manchester almost one in five fifth-formers leave without a grade.

One of the Government’s advisers on interpreting exam results, Carol Fitz-Gibbon, professor of education at the University of Newcastle, believes the performance tables are encouraging schools to target those pupils that are most likely to boost their ranking in the tables.

A number of schools with below-average results admit that since the publication of national tables they have put extra effort into encouraging pupils identified as having a chance of achieving a grade C at GCSE.

She says: “Manipulation is happening all over and it is very unfair. You can’t draw a line and say A to C grades are more important, you should use a point system that values everyone equally.”

Overall, 43.5 per cent of 15-year-olds gained five or more GCSEs at grades A* to C, compared with 43.3 per cent last year and 41.5 per cent in 1993. The proportion of pupils gaining five or more at grades A* to G increased marginally from 85.6 to 85.7 per cent.

At 78 schools the whole fifth-form gained five GCSEs at C and above. These schools are all either independent or operate some form of selection. Grant-maintained schools outperform local authority schools, but the sector has a higher proportion of grammars than the rest of the state system.

The exercise was hailed by the Government as a remarkable achievement in providing information to parents on educational institutions and as a means of driving up standards.

The relative performance of local authorities has changed little in the four years the tables have been published. Kingston upon Thames, where 55.5 per cent of pupils gained five or more higher grade GCSEs, tops the league, but it has always been in the top five.

The inner London borough of Islington comes bottom with only 17.4 per cent of fifth-formers with five or more higher grade GCSEs. It has always come well down the table. The two large urban education authorities with the worst results are Manchester, where 22.5 per cent of pupils achieved five or more grade Cs and above and Liverpool, where 26.1 per cent of pupils achieved that benchmark.

Poor exam results tend to be linked to high truancy rates. The school with the highest absence rate is Battersea Technology College in Wandsworth, one of 26 secondary schools judged by the Office for Standards in Education to be failing to provide an adequate education. The Amy Johnson school in Humberside, where no pupils achieved five or more higher-grade GCSEs, is one of the 20 schools with the highest absence scores.

Also in the top 20 are four other failing schools. One is Hackney Downs, the first school to be closed by the Government. Its pupils are to be transferred to Homerton, which records only marginally better truancy figures.

Teachers’ unions remain implacably opposed to the tables in their present form and called once again for the introduction of a measure of “value added”. David Hart, general secretary of the National Association of Head Teachers, called the tables “sterile” and said that the emphasis on five or more A* to C grades as a performance indicator encourages schools to abandon the pupils who look unlikely to make these grades. “There is already evidence that the ‘long tail of underperformance’ will lengthen for those who cannot achieve pass grades. This would be an unforeseen yet highly damaging consequence of league tables in their present form.”

Doug McAvoy, general secretary of the National Union of Teachers, said: “Now that the statistical base has been exposed as flawed, the Government should end this failed ranking system.”

The Liberal Democrat education spokesman, Don Foster, wants the performance tables abolished until the Government is able to produce value-added tables. He said: “It is vital that parents receive information about their children’s progress and the schools they attend. But that information must be useful, accurate, comprehensive and understandable.”