England's schools are to receive an extra £350m in 2015-16 - but the government has abandoned its plans to introduce a national funding formula before the general election.
This means schools in different local authority areas will continue to receive different amounts per pupil.
Schools Minister David Laws said 40% of these areas would gain funding in 2015-16 and none would have less per pupil.
Labour said it was not clear where the new money would be coming from.
Mr Laws highlighted the fact a school in Birmingham in which only 3% of children were eligible for free school meals currently received more money per pupil than one in Shropshire where nearly 33% qualified for FSM.
But he said steps taken in 2013-14 and 2014-15 meant the system was already fairer - with 80% of funds now allocated on the basis of pupil numbers alone - and his department was now taking "the first huge step towards delivering this fairer national funding".
Announcing the extra £350m, Mr Laws told the Commons: "This will be the first time in a decade that funding has been allocated to local areas on the basis of the actual characteristics of their pupils and schools, rather than simply on the basis of historic levels of spending."
But he added: "Given the importance to schools of stability and certainty in these difficult economic times, we have decided not to set out a multi-year process of converging all local authorities towards a single funding formula.
"We have concluded that the right time to do this would be when there are multi-year public spending plans, so we can give greater certainty to schools.
"But the case for action is so strong that we intend to act immediately to deliver a substantial £350m boost to schools in the least fairly funded local authorities in the country.
"We will be able to achieve this without any local authority receiving a cut to its per-pupil schools budget."
Mr Laws also announced a minimum funding level for schools would be set, again for 2015-16 alone.
This would be based on the number of pupils and the proportions who were poor, spoke English as a second language, had low attainment levels entering school, or had been looked after in the care system, he said.
National Association of Head Teachers general secretary Russell Hobby said: "This is a small step towards a fair national funding formula.
"We urge the government to continue the journey."
He added: "Cost pressures on schools are growing severe and we are staring at more redundancies without increases in funding.
"The simultaneous announcement of additional employer pension contributions only adds to the pressure.
Shadow schools minister Kevin Brennan, said: "The discussion about a fairer funding system should begin with a look at the way the [Prime Minister David] Cameron has allocated funding for new school places.
"According to the National Audit Office data, overall, two-thirds of all places created by the free schools programme are being diverted away from areas of high and severe need for primary places.
"This is a scandal when we have a primary places crisis."
Association of Teacher and Lecturers director of economic strategy and negotiation Martin Freedman said: "This government has been in power for four years, yet has done nothing to ensure funding for schools is made fairer.
"For all David Laws's hand wringing about unfairness and the government once again promising that it is about to take the 'first huge steps', nothing is going to happen until after the general election."