The myth that London schools are underperforming has been exploded by new figures which show they are outshining schools in the rest of England.

Today’s revelation comes in the week it emerged that left-wing Labour MP Diane Abbott has rejected a local state secondary and sent her 12-year-old son to the pound;10,000-a-year City of London School. It also follows claims by Oliver Letwin, Conservative shadow home secretary, that he would rather “go out on the street and beg” than send his children to state schools in Lambeth.

London schools commissioner Professor Tim Brighouse has revealed new figures to The TES which divide schools’ provisional GCSE results for this year into 10 bands according to the percentage of pupils eligible for free school meals.

In every band the proportion of pupils getting five Cs or better at GCSE was higher in London.

A MORI poll to be published later this autumn will show that parents in London usually believe that education is worse in the capital than elsewhere.

However, the poll will also show that parents who do send their children to the city’s state schools are more satisfied than the national average.

Professor Brighouse said the new data proved that MPs’ fears about the standards of London schools were based on myth rather than reality.

He said that he was “extremely sad” that people opted out of the state system. “I think people who make that choice sometimes subsequently have an uneasy conscience about their decision and that is totally understandable.

But it is no reason for them to talk down the achievements which the rest of us are enjoying.

“My experience in putting my children through urban schools is that they achieve in a vivid and rich environment that is determinedly improving its performance.”

Professor Brighouse said the analysis backed his own findings since becoming commissioner. He had visited more than 100 London schools and found that around two-thirds had a very strong achievement culture, a pattern that he suspected was replicated in other big cities. However, Chartered Institute of Public Finance and Accountancy figures this week show that spending on pupils in London schools is 17 per cent higher than the national average.

Ms Abbott, MP for Hackney North and Stoke Newington, was labelled a hypocrite this week after newspapers reported that she criticised Tony Blair for rejecting Islington schools in favour of the London Oratory school.

The MP has refused to comment on her decision. But her son James defended her in a radio interview in which he said that it had been his choice to attend the private school.

Ms Abbott was also defended by Trevor Phillips, chairman of the Commission for Racial Equality, who faced similar criticism when he sent his daughters to the fee-charging North London Collegiate school.

Professor Brighouse said myths about state education in London had grown up partly because of the high concentration of politicians and journalists living in the capital.

He said he thought they “kept themselves warm at night” by recounting the horror stories they had read in the media.

John Bangs, head of education for the National Union of Teachers, said that London schools were performing better than the public perception because the city was a “magnet for very good teachers”.