The chief inspector of schools has defended Ofsted’s work, saying it was “absolutely not” underperforming.

Amanda Spielman’s comments came as the independent body that grades schools in England found itself on the receiving end of unfavourable scrutiny by government inspectors after MPs said it required improvement to avoid losing credibility.

The report by the House of Commons’ public accounts committee was critical of Ofsted’s effectiveness in recent years under Spielman and her predecessor, Michael Wilshaw, saying its inspection programme was struggling under deep funding cuts, high staff turnover and flawed policies.

Ofsted’s school inspections budget had been slashed by more than 50% since 1999, which had “undermined families’ ability to make informed decisions about schools”, according to Meg Hillier, the committee’s chair.

Spielman told BBC Radio 4’s Today programme that the agency did not “recognise this picture” painted by the report.

Asked if she had fallen out with the committee because she would not say funding cuts were affecting educational standards, Spielman replied: “We haven’t seen anything yet from school inspections that says that schools are unable to provide a good quality of education by reason of funding.

“We know there are many things that affect the allocation decisions that schools make. What we haven’t seen is any evidence from what we do that says reductions in school spending are responsible for that.

“It makes wonderful headlines when chief inspectors express opinions that aren’t backed up by their evidence, but it doesn’t make for such good decisions.”

Chris Keates, the general secretary of the NASUWT teaching union, said the government’s actions had been “entirely wrong” over the past 10 years, “slashing Ofsted’s budget without any reference whatsoever to the wide range of important responsibilities that it has to discharge”.

MPs on the committee said they were disappointed at Spielman’s reluctance to criticise the government over issues such as school funding, with Hillier saying the inspectorate risked becoming “simply a fig leaf for government failures”.

“Championing standards is an important part of any independent inspector’s remit, and we were disappointed that Her Majesty’s chief inspector seemed reluctant to offer her views about wider issues affecting the school system,” the Labour MP said.

Noting the committee’s “disappointment”, Spielman told the MPs: “My role is to provide parliament and the secretary of state with an evidence-based appraisal of educational standards. It would be irresponsible of me to make comment on those areas where we do not have clear evidence of the impact on standards or young people’s wellbeing.”

The committee was highly critical of the number of schools exempted from regular visits by Ofsted inspectors, saying it was “unacceptable” that hundreds of educational establishments rated by inspectors as outstanding could avoid scrutiny for a decade.

“As a result, some pupils go through the whole of primary and secondary school without any independent assessment of their school’s effectiveness. It is reasonable to assume that not all these schools remain at the same level of performance after so many years,” the committee reported.

It ordered the Department for Education to look at why outstanding schools were exempt from routine reinspection and report back. The exemption was brought in under Michael Gove in 2011.

Geoff Barton, the general secretary of the Association of School and College Leaders, said: “It is important that the public understands that there is no lack of scrutiny of schools and that, if anything, they are creaking under the strain of excessive scrutiny from multiple directions.”

The committee criticised Ofsted for providing erroneous figures on whether all eligible schools had been inspected during a year, when it had actually failed to meet its targets.

“It is not encouraging that Ofsted also misinformed parliament about the inspections it had carried out – a mistake that further calls into question its effectiveness,” Hillier said.