The government’s flagship policies for improving schools – encouraging them to convert to academy status and establishing free schools – have had little or no effect, according to a major parliamentary inquiry to be published this week.

On Wednesday, the House of Commons’ education committee is expected to offer an embarrassingly tepid verdict on the government’s academy and free school programmes, including evidence that the impact on raising school performance of its multibillion-pound converter academy programme is “inconclusive”.

The investigation by a bipartisan committee of MPs will be seized upon by Labour, which hopes to open a second front in the election campaign after the success of its attacks over NHS funding.

Tristram Hunt, the shadow education secretary, said in an interview with the Guardian that the government was undoing the improvements that had taken place in state schools in England through its obsession with imposing a market-based ideology in education.

The education committee report is expected to be most damaging in drawing a contrast between the results of converter academies – schools that voluntarily converted to academy status through policies introduced by Michael Gove in 2010 – and Labour’s earlier sponsored academy programme, which sought to turn around struggling schools.

The MPs took evidence from policymakers and considered data on exam performance in judging the effectiveness of different types of schools.

Once adjusted for prior attainment, however, it found that converter academies did less well than sponsored academies.

The latter have been praised by Sir Michael Wilshaw, Ofsted’s chief inspector, for raising education performance at a faster rate than other schools.

The committee’s report will also be highly critical of the Department for Education’s oversight of academies, which deal directly with Whitehall.

It will call for the Education Funding Agency, the section of the DfE that oversees academy finances, to be split into different units, with one to focus specifically on financial accountability.

Hunt said: “It is undeniable that the last Labour government dramatically improved school standards in secondary education. When he was not seeking to make cheap political capital, even Michael Gove admitted this.

“But the progress that we made – through the sponsored academy programme, through record investment and reform in our schools, by raising the bar on what we expect from teachers – is being undone by a government that is obsessed with a market ideology in education.

“But while the Tories have spent nearly five years talking down our schools system, they have simultaneously undone the progress that has been made, watering down teaching standards and the expectations of headteachers. These moves are disastrous, storing up problems for the future.”

A DfE source said Hunt did not appear to understand that sponsored academies would improve faster because they had further to go, while converter academies are already good or outstanding schools where academisation was designed to reward them for their success.

“It is of course nonsense to claim we’re undoing all their good work,” the source said. “While we have a million more children being taught in good or outstanding schools, 100,000 more six-year-olds able to read because of the focus on phonics and a 60% increase in the proportion of children studying core academic subjects at GCSE, they left a legacy of falling standards where a third of all children left primary school unable to read, write or add up properly and Britain was stagnating in international league tables while the rest of the world moved on.”

Education secretary Nicky Morgan also faces further embarrassment after her high-profile consultation exercise on teacher workload – which she unveiled at last year’s Conservative party conference – found that teachers named “government policy” as a main cause of extra work in state schools.

A confidential briefing paper on the results of the teachers’ “workload challenge” circulated within the DfE revealed that “government policies, including insufficient lead-in time for new policies; high stake demands of accountability systems; and pace and scale of change” was the first of three main areas of complaint.

The workload challenge was launched with great fanfare by Morgan in October and was seen as a means of rebuilding bridges with the teaching profession after Gove’s departure.

Senior teachers say their workload has become heavier as a result of the rapid introduction of new GCSE and A-level courses, while national curriculum revisions and changes to the scale and depth of inspections by Ofsted have made matters worse.

The discussion document – which has not been circulated to ministers – suggests a rule that would delay the start of “complex reforms” by at least a year, and more extensive testing of new policies through trials in small numbers of schools before national implementation.

Hunt accused Morgan of “political chicanery” over the results of the workload challenge, which drew replies from more than 20,000 teachers and was applauded by the main teaching unions. But the full results appear unlikely to be published before the general election in May.

“She has admitted herself in this paper that her department is to blame for the increase in teacher workload,” he said.

“But voters will see this political posturing for what it is: a desperate attempt by the Tories to undo the damage that Michael [Gove] has done and the electoral price that they will pay for it.”