Houses could be built on land set aside for a new secondary school in Croxley Green.

Transport for London owns the land to the north of Baldwins Lane, which has been earmarked for the Croxley Green Secondary School.

Hertfordshire County Council has been trying to buy the 30-acre site worth £3.5million for two years.

But TFL claims the land could be used as a “mixed development” – opening up the possibility of houses and shops being built on the site alongside a new school. One Three Rivers District Councillor fears as many as 300-400 houses could be built on the site if the site was houses alone.

Graeme Craig, Director of Commercial Development at Transport for London (TfL), said: “We have been in discussions with Hertfordshire County Council about a suitable scheme for the site, which could include a mixed use development incorporating a school.”

Mr Craig did not comment on how many houses this could include.

The council refused to be drawn on whether the land price could increase but stressed negotiations are being concluded “as quickly as possible”.

The authority believes the Croxley Green Secondary School is key to reducing pressure on school places.

Figures released by Hertfordshire County Council show1,396 pupils will need a secondary school place in Watford and in 2019, there will be a shortage of 165 places, with nearly 1,500 pupils needing a secondary school place.

In Rickmansworth, there will be shortage of 19 places in 2017, 58 places in 2018 and 52 places in 2019, if no additional places are created.

When the county’s policy, resources and transformation committee approved the buying of the land in 2013, it did so on the basis that “the case for additional secondary school places in south west Hertfordshire is so strong and the site is so suitable to meet part of that need that the county council is able to show there is a ‘compelling case in the public interest’ for its acquisition.”

Spokesman for Hertfordshire County Council Andrew Dawson said: “The Department for Education has advised the Croxley Green Secondary School that its proposal to open a new secondary school at Baldwins Lane in Croxley Green can progress to the pre-opening phase.

“This approval for an opening in 2017 is conditional on Hertfordshire County Council funding the acquisition of the site, which has been allocated for education use by Three Rivers District Council.

“It wouldn’t be appropriate for us to comment on any views TfL may have.

“Our aim is to ensure that any land acquired can accommodate a school that will be able to meet anticipated demand for school places both now and in the future.”

“We are working hard to conclude negotiations as quickly as possible. The opening of the new school is a matter for the EFA and the Trust.”