Over the past 20 years Government spending on schools in England has become increasingly focused on facilities with pupils from poorer backgrounds, according to the IFS.

In 2013/14, spending per pupil in the 20% of secondary schools with the poorest pupils (£7,400) was £1,800 more than spending per pupil in the richest 20% (£5,600).

This gap in funding, researchers from the Institute of Fiscal Studies say, is double what it was in the late 1990s. It is roughly 30% now as opposed to the 15% it was 20 years ago.

For primary schools this difference has grown from 10% to 25%.

The IFS’ findings, published in a report funded by the Nuffield Foundation, also reveals a lot of variation in funding between schools with similar pupil intakes.

Among the 20% poorest schools, 10% spent more than £9,000 per pupil while 10% spent below £6,200.

One of the primary reasons for this, according to the IFS, is that local authorities currently have the power to make different choices in the way schools are funded in their areas.

The IFS argue a national formula to determine school funding, which has been proposed by the Government, would eradicate the differences in spending per pupil within individual local authorities, but would do little to close the gap in funding between wealthier and poorer schools.

Such a national formula would, however, mean a loss of discretion for local authorities to respond to particular local circumstances.

Chris Belfield, one of the authors of the report, said: ‘Over the past two decades, school spending has become increasingly targeted at the schools with the most deprived intakes; the Pupil Premium continued rather than started this trend.

‘This represents a major shift in the role of the state, with the school funding system playing an increasingly important role in redistribution.’

Luke Sibieta, the other author of the report, added: ‘The introduction of a national funding formula for schools in England looks set to be one of the most radical shake-ups of school funding in at least the past 30 years.

‘Replacing 152 different formulae with one single, simple formula will inevitably lead to substantial changes in funding across schools and, for good or bad, will almost completely remove local authorities from the school funding system.’