More than half a billion pounds is to be pumped into creating new free schools, including grammars, and refurbishing existing school buildings, the Government has said.

Chancellor Philip Hammond's Budget will include £320 million to help fund up to 140 new schools, creating more than 70,000 new places.

The investment is intended to build on the Government's commitment to open 500 new free schools by 2020, he is expected to announce tomorrow (Wednesday).

The move follows on from Prime Minister Theresa May's pledge last autumn to create a place at a good school for every child, in part through allowing selective schools to expand and new ones to open.

It is understood that the Government has not set a target on the number of grammar schools it wants to open with this new funding, but is open to these selective institutions submitting proposals.

The money includes funding for more specialist maths colleges, such as the existing Exeter Mathematics School - which selects 16 to 19-year-olds based on their aptitude for the subject.

Of the 140 new free schools, 20 will open by 2020, and the majority of the rest will open over the course of the next parliament.

There are currently 431 open free schools - a key plan of Conservative education reform - and a further 243 in the process of opening.

The Budget will also include a further £216 million to rebuild and refurbish existing schools in England, to ensure that they are fit for purpose.

This money is on top of existing plans to spend more than £10 billion on school buildings over the course of this Parliament.

And the current entitlement for children who access free home-to-school travel will be expanded to cover selective schools.

Mrs May said: 'For too many children, a good school place remains out of reach, with their options determined by where they live or how much money their parents have.

'Over the last six years we have overseen a revolution in our schools system and we have raised standards and opportunity, but there is much more to do.

'As part of our commitment to creating a school system that works for everyone, today we are confirming new investment to give parents a greater choice of a good school place for their child, and we will set out the next stage of our ambitions in the coming months.'

Mr Hammond said: 'Investing in education and skills is the single most important thing that we can do to equip our children for the future.

'We are not starting from scratch; we have protected the core schools budget, which stands at over £40 billion this year, and these announcements take the next steps in giving parents greater choice in finding a good school for their child, whatever their background.'

The funding announcement comes just weeks after a spending watchdog warned that the Government is pouring billions into building new free schools in England while existing state schools are crumbling due to lack of repairs.

The National Audit Office (NAO) said £6.7 billion was needed just to bring all existing school buildings up to a 'satisfactory' standard, with a further £7.1 billion required to restore them to a 'good' condition.

Dr Mary Bousted, general secretary of the Association of Teachers and Lecturers, said: 'Teachers and heads in the thousands of existing state schools in the UK which are facing real-terms cuts in funding for their pupils will be dismayed to see the Chancellor throwing more money at free schools and grammar schools.

'It will do nothing to help schools recruit and retain teachers and heads, and will put a broad and balanced curriculum at risk.'