State schools should benefit from the same tax breaks given to the independent sector, a senior MSP has suggested.

Jackson Carlaw, deputy leader of the Scottish Conservatives, raised the idea as he opposed a petition to strip independent schools of their controversial charitable status, which amounts to tax relief worth about pound;4 million a year, according to the Scottish Council of Independent Schools (SCIS). The West of Scotland MSP argued that rather than preventing private schools from operating as charities, the status should be widened to include local authority schools.

His proposal came as SNP MSP David Torrance said that cash-strapped councils were already exploring the idea of turning their schools into charities.

More than 300 people have signed a petition to strip private schools of their charitable status, which was debated for the first time in Parliament this week. It was lodged by political campaigner Ashley Husband Powton and calls on the Scottish government to abolish the “unfair financial advantage” accorded to the private sector through vast reductions on non-domestic rates. She also claims that independent schools do not meet new, stricter criteria for charities because they fail to benefit “99 per cent” of the population.

Disputing that criticism, Mr Carlaw asked Ms Husband Powton: “Would it not be the right move to allow state schools to have these benefits extended to them as well?”

Ms Husband Powton, who gave evidence to the committee on Tuesday from her Orkney home via a video link, responded: “I agree that state schools should have charitable status but I still think it should be removed from private schools. I would call for a complete reversal, taking it away from private schools and giving it to state schools.”

Mr Torrance, SNP member for Kirkcaldy in Fife, told the committee: “Local authorities have moved sports, leisure, arts and libraries into charitable status and are now considering moving some of their schools into charitable status.”

The Office of the Scottish Charity Regulator (OSCR) has been reviewing all fee-charging schools in Scotland after 2005 legislation led to the introduction of what the independent sector has branded the “toughest” charity test in the world.

The SCIS refuted campaigners’ claims that schools had changed their policies out of “coercion” from the regulator to meet the higher public benefit standards, rather than in the “spirit of charity”.

SCIS director John Edward said: “I think the planning process that our schools and the regulator have gone through has been very constructive in the end.

“All our schools are proud of their charitable status, which in some cases goes back centuries. [The 2005 Act] made them rethink their charitable purpose and see what else they could do.”

He also dismissed claims that the government could save money by removing charitable status from independents, saying that the pound;4 million a year that private schools gained in tax relief was far outweighed by the 10 times that they invested, mostly in bursaries funded by fees from parents.

State schools effectively did not pay full rates either, he added, because they were funded by the same councils that “billed” them, resulting in a “paper exercise”.

Scotland’s largest teaching union, the EIS, has approved a motion calling for charitable status to be removed from private schools, amid growing concern over the fairness of granting “potentially preferential financial treatment” to a handful of educational establishments, as most others face “considerable financial strain”.

However, a spokeswoman said the EIS executive committee was consulting members before deciding its policy position.

Local authorities body Cosla said it had “no position” on the issue of charitable status. Meanwhile, an OSCR spokesman warned that any move to award the same charitable status to the state sector would be “a major undertaking” given the number of state schools in Scotland.

Earlier this year, former politician Jim Sillars, who represented both the SNP and Labour, said that state schools deserved charitable status.

The petitions committee will invite the EIS, OSCR and Cosla to give evidence on the “practical consequences” of revoking private schools’ charitable status.