Statistics obtained by David Blunkett, the shadow education secretary, in written replies to parliamentary questions show that 20 per cent of pupils in LEA secondaries are eligible for free school meals, compared with 13 per cent in their GM counterparts.

In the primary sector, 22 per cent of pupils in LEAs qualified for free meals, while just 16 per cent did so in opted-out primaries. Analysis of the figures by the advisory body Local Schools Information reveals that overall, while 20 per cent of pupils in LEA secondaries were on free school meals, 38.7 per cent gained five or more top grades at GCSE.

In the grant-maintained sector, 44.7 per cent of pupils gained five or more GCSEs grades A to C, but just 13 per cent were eligible for free meals. But in authorities with a similar proportion of pupils on free meals in both GM and LEA secondaries, there was no significant difference in exam performance.

Martin Rogers, from LSI, said: “The fact that GM schools have a more privileged intake and a higher level of funding yet perform only marginally better than LEA schools calls into question the whole thrust of present schools policy.”