Andy Burnham will accuse the Government of breaking a promise not to cut school funding.
In a speech to the NASUWT annual conference in Glasgow, the shadow education secretary will claim that the schools budget is going to fall every year for the next three years.
He will claim that an analysis based on figures from the House of Commons library show that budgets will be cut by 1.1% in real terms between 2010/11 and 2014/15, with per-pupil funding falling by 3.9%.
Mr Burnham will tell delegates: "This Tory-led Government's education policy consists of broken promises, incompetence and wrong-headed reforms.
"They said they had found more resources for schools - but the schools budget is going to fall every year for the next three years. This is alongside cuts of 80% to budgets for maintenance and repairs next year.
"Increasingly, we are seeing the sort of poor decision-making and lack of clarity from central Government that can only be called incompetence - like the last-minute cut of £155 million from school budgets.
"This will mean schools losing money they have already been allocated in the middle of an academic year - or facing an even tighter financial settlement next year."
In his spending review statement last year, Chancellor George Osborne said: "There will be a real increase in the money for schools, not just next year or the year after - as the last government once promised - but for each of the next four years. The schools budget will rise from £35 billion to £39 billion."
A Department for Education spokesman said: "We are protecting school funding in the system at flat cash per pupil before adding the pupil premium. Flat cash per pupil means that, as pupil numbers go up, the overall budget goes up in line.
"We are putting money directly in heads' hands and cutting central bureaucracy to protect the front line. The current school funding system is illogical, unfair and opaque. That is why we recently launched a consultation to address the disparities and inequalities within our current system."
