The UK can no longer claim to offer a world-class education system, a comparison of international achievement among 15-year-olds suggests.

Standards of reading and maths have fallen to such an extent that the UK has fallen out of the top-ten of ranked countries, making it the only country previously ranked above-average to drop out of the top performing group.

According to the Organisation for Economic Co-operation and Development’s (OECD) analysis, the UK is now ranked 24th in the world for maths, down from eighth in 2000, and 17th for reading, down from seventh at the turn of the millennium.

The latest analysis of Programme for International Student Assessment (Pisa) performance tables follows on from the finding last week that the UK’s has lost its top-five science ranking, falling from fourth to 14th in the world.

The Pisa tables are compiled every three years to compare education standards among the world’s 15-year-olds.

Today’s figures come as the government attempts to gain cross-party support for its education and skills bill, which will raise the education leaving age to 18.

Gordon Brown insists this is necessary to make the UK a world-class education system.

Responding to the drop in rankings, schools minister Jim Knight said today that the UK is still above average.

But he said the government was prepared to intervene when children were falling behind: “We are putting a relentless focus on the progress of every individual through programmes such as Every Child Counts and personalised learning so that we know exactly where progress is made and where children are falling behind.”

However, the Liberal Democrats said the OECD report showed UK children are shortchanged compared to their global counterparts, with performance going down despite investment.

Lib Dem schools spokesman David Laws said: “This is a real blow to a government that has promised to improve education.”

He added: “This should prompt a fundamental review of our education policy to explain why we are failing to do as well as other countries.”

The Conservatives said the report undermined the government’s claim to be raising educational standards.

Shadow education secretary Michael Gove said: “Every year the government boasts about the improvements it has made to education but every external audit tells us we’re falling further behind.”

Mr Gove said education secretary Ed Balls’ failure to reform a “complacent” educational establishment was now “condemning future generations to further failure”.