Parents of children at Our Lady of Lourdes primary school had applied to the High Court for a judicial review against Brentwood Diocese, which oversees the administration of all Catholic schools in the area.

But they feel they have been "priced out" of proceeding any further with legal action and cannot continue to fight the academisation proposals.

A spokeswoman for the group said: "The feeling among the campaign group is that we don't need to proceed further and waste thousands of pounds doing so.

"No one ever wanted to take legal action but when you are consistently met with silence and delay tactics to force through the academisation, what do you do?

"Parents deserve a voice and that voice to be heard.

"I hope both the school and diocese learn from this because it is our children's lives they are playing with."

Brentwood Diocese said its steering group has been "committed to making its proposals as transparent as possible, consulting widely and sharing the vision with local authorities".

But Paul Donovan, councillor for Wanstead Village, said parents have been treated "very poorly" by the diocese.

"It is a great shame that the parents have been forced to go to these lengths in order to get a proper consultation out of the diocese," he said.

"This has still not happened, with the school seemingly marching onto academisation.

"It is a great credit to the parents that they have fought so long and hard for the wellbeing of their children and the school.

"Redbridge Council has tried to point out that it is better for schools to remain in partnership with the local authority, however, this advice has clearly fallen on deaf ears.

"Our Lady of Lourdes school has an excellent reputation for the education it has provided within the embrace of the local authority.

"The question asked before remains unanswered, namely, if it isn't broken, why change it?"

John Anthony, chairman of the Good Shepherd Trust, the trust which Our Lady of Lourdes will be joining, denied that parents involved in the legal proceedings were "priced out of it".

He said: "Neither the school nor the diocese instituted any legal action, they were merely responding to it - the action so far has cost the school a great deal of money that should have been better been on education.

"The 'wellbeing' of children at the school has not been affected in the slightest."

Mr Anthony also pointed out the school has previously said "it was a great shame that this success is marred by the adverse publicity in both the national and local press, which detracts from the work of children and teachers at the school. Surely such efforts could better be directed against school funding cuts across the local schools".

Rob Simpson, Brentwood Diocese's education director, said bringing schools together in a Catholic multi-academy trust is about "local groups of schools supporting each other with a common ethos and values".

"We are not talking about running a CMAT as a business, although there would be financial benefits through economies of scale and the opportunity to provide more or retain resources," he said.

"It is about local groups of schools supporting each other with a common ethos and values, and the opportunity to aid career development, recruitment and retention. There will be no change to staff pay and conditions.

"All of our schools - whether voluntary aided or academy - will continue to have governing bodies that are responsible for maintaining high standards and protecting the distinctiveness of each of our schools.

"We place an emphasis on ensuring that there is both parental and staff involvement in the governance of the schools.

"We wish to maintain a positive working relationship with each local authority and for our schools to work collaboratively with Catholic as well as other local schools."