Campaigners have put on hold a legal challenge to a decision by the government to approve a new grammar school annexe in Kent.

The campaign group Comprehensive Future had been expected to announce whether it was pressing ahead with a judicial review of the decision this week.

But in a statement it said it needed more information before deciding what to do.

Education secretary Nicky Morgan last year gave the green light for the annexe to be built at Sevenoaks, sponsored by the Weald of Kent Girls Grammar School.

The decision came after a lengthy campaign launched by parents in the area, who said pupils had to travel long distances to take up grammar school places.

Comprehensive Future said in its statement the government had rejected requests for more detailed information about the decision, making it harder to push ahead with a legal challenge.

It said: “In the past few months, Comprehensive Future has requested information from the government, Kent County Council and the school in order to test the legal basis of this claim. "Information has often not been forthcoming or has been unaccountably delayed."

The statement continued: “Those plans that CF [Comprehensive Future] has been allowed to see appear to be highly impracticable and are unlikely to be sustained over the long term but the government has forbidden us to discuss these publicly.”

The group says the lack of openness “has made it almost impossible for us to be certain of legally establishing, at this stage, that this is indeed a new school.”

"Information has often not been forthcoming or has been unaccountably delayed,” - Comprehensive Future

But it adds: “CF intends to keep a close eye on the development of the so called annex. In particular, we will be scrutinising details of the school’s plans when published in the funding agreement.

"We believe we are much more likely to win any legal argument when all the information pertaining to the day-to-day running of the school is out in the open.”

It ends by saying there needed to be robust public discussion about whether Sevenoaks “really is an annex of an existing school or whether the current plans are, as we believe, a concerted and blatantly political attempt to get round the law.”

Meanwhile, a newly-formed think tank, Kent Education Network, which opposes selection, said the new annexe would not work.

Spokesman Joanne Bartley said: "It is obvious that huge costs would be incurred in staff travel and that many more staff members would be required for the school to provide a full teaching programme. The only way to tackle this problem would be for the "school" to be divided horizontally so that senior pupils attend one location while juniors are based at the other."

"This would have two effects: such an arrangement could not be described as "one school"; and, further, at least half of the combined school cohorts would need to make the ten mile journey twice a day. This would contradict the intended point of the annexe plan – which is that these journeys should be ended. It would also mean that many children from the Tonbridge area would make these journeys for the first time."

Sevenoaks MP Michael Fallon welcomed the news as a sign that the plan would not be delayed by court action.

"It would have been outrageous for politically motivated national campaigners to attempt to block the expansion of a successful school" -Sevenoaks MP Michael Fallon

"It would have been outrageous for politically motivated national campaigners to attempt to block the expansion of a successful school that is strongly backed by the people of Sevenoaks and Kent County Council."

"I welcome the news that the annexe can now start to be built,meaning that local parents will at last have the same choice of schools as elsewhere in Kent."

Parents who campaigned for the satellite grammar, said a legal challenge was now unlikely.

Andrew Shilling, who led the campaign, said the opponents had beaten a humiliating retreat and took a sideswipe at the group Comprehensive Future.

"This is excellent news because the threat of a legal challenge has now been permanently lifted. The annexe for girls can now be built without further delay. The builders are now on site and so the annexe can be expected to open its doors in September 2017."

"This empty threat of a legal challenge was therefore in my view based on a dodgy dossier of nonsense, and so was always doomed to failure" - campaigner for annex Andrew Shilling

"The grammar annexe in Sevenoaks is not the new school that this privileged North London clique allege because, quite simply, if it was then it would admit Sevenoaks boys who also desperately need local grammar places, and not just girls."

"This empty threat of a legal challenge was therefore in my view based on a dodgy dossier of nonsense, and so was always doomed to failure."

The new annexe would be at the former Wildernesse School, which it would share with a free school.