Only 17.4 per cent of 15-year-olds in Islington gained five GCSEs at grade C or above. This compares with the national average of 43.5 per cent. The borough also has double the number of 15-year-olds who fail to achieve even one GCSE, compared with the national average.

The council was in the news earlier this year when it was revealed that Tony Blair, the Labour leader, was sending his son to the London Oratory, a grant-maintained school eight miles outside the borough where they live. The league tables show that 62 per cent of 15-year-olds at the London Oratory gained five GCSEs at C and above, compared with 18 per cent at St Aloysius’ College, the Roman Catholic comprehensive closest to the Blair household.

Hilary Nicolle, Islington’s education director, said the results were disappointing: “Being bottom will give us a further impetus to make improvements. We now have in place totally committed headteachers who are real partners in projects with the council to raise standards in the classroom. ”

She said parents were entitled to raw results, but said further information must be available. “It can be very upsetting to parents to read that their children are in the worst borough, but it must be pointed out that some pupils are doing very well.”

The smaller boroughs argue that their results are particularly susceptible to fluctuation. Islington has nine schools and says that problems in two this year have had a dramatic effect on its overall score.

The council says it does not want to make excuses, but points out: Islington is the fourth most deprived area in England; the number of pupils eligible for free meals in Year 11 jumped from 46.6 per cent to 51.5 per cent; and the borough has more boys than girls in Year 11, and boys perform less well than girls at GCSE.

By January, there will be seven new heads in place and several initiatives will be under way. All secondary schools have agreed to take part in the Improving Pupil Achievement Project, which concentrates on improving GCSE grades.