Britain has the biggest primary school classes in the developed world, a new report has revealed.

State primary schools in the UK now have an average of 28 pupils, according to the Organisation for Economic Co-operation and Development's (OECD) latest Education at a Glance study.

This is the first year that Britain has been ranked as having the highest number of pupils per class – joint with Chile – out of all the OECD countries.

The report, which looks at the state of education systems across 36 nations with developed economies, plus ten other partner countries, found that the average class size for state primary schools in OECD countries is 21 children.

The UK is followed by Israel and Japan, which have an average primary school class size of 27 children. Meanwhile the countries with the smallest primary class size are Costa Rica and Luxembourg which have an average of 15 children.

Primary school class sizes in the UK have been under pressure in recent years following a boom in pupil numbers caused in part by a rise in the birth rate in the early 2000s, which is now making its way through to secondary schools.

While direct immigration has little effect on pupil numbers, higher birth rates among immigrant communities has been a contributing factor, according to official forecasts.