MP Tom Brake has demanded his Liberal Democrat colleagues on Sutton Council explain how they will provide more school places after they moved to block a new secondary at Rosehill Park.

Council leader Ruth Dombey announced on Friday her councillors would veto the construction, after the Education Funding Agency said it favoured a new school in Rosehill, and snubbed the council's £8m investment in an old Sutton Hospital building in Belmont.

Coun Dombey claimed the move was a "common sense decision to protect our green spaces as much as possible".

The EFA made its decision in July.

But Mr Brake said today: "There's very clearly pressure on school places, with a need to provide a new school by 2017. I want to hear from Sutton Council how that's going to be achieved.

"The council will now have to redouble their efforts to make sure those places are available in 2017. The priority is to make those school places available."

Paul Scully, Conservative MP for Sutton and Cheam, said: "Persisting with jamming a school onto the Belmont site that every study has said is one-fifth of the required size, is foolhardy in the extreme.

"Unless the council see sense, there is a real possibility that they will not meet their own target to open a new school by September 2017, which will lead to children without a secondary school place in the borough."

Mr Scully used his first speech in the House of Commons to give his support to the Rosehill Park option, and has argued the Sutton Hospital site is too small to satisfy future demand for school places.

Lib Dems hope the Belmont site could be used for a new school and part of a cancer research centre.

Coun Dombey added in a statement released by Sutton Council's press office: "The potential to connect a secondary school to what could be the second largest life science cluster in the world is a once-in-a-lifetime opportunity that would create a ladder of opportunity for our young people.

"Even if the hub did not go ahead, we would still be using a brownfield site instead of a green space which has to be the preference for Sutton.

"We are a green council and we are working to make the borough a more attractive and more sustainable place."

In a letter to the EFA, education committee chairman Coun Wendy Mathys admitted the stance "may set back the timetable for the new secondary school" but touted "our exciting plans for the new cancer hub".

She added: "The Institute of Cancer Research have expressed great interest in engaging with the school particularly over sharing sports and science facilities."

Alan Trickey, chairman of the Sutton Hospital Action Group (SHAG), said: "It should be remembered that Sutton Council indicated that they would go along with the site chosen by the EFA and Greenshaw.

"Now they are going back on their word, putting a spin on a diabolical decision which will adversely affect the education of our children."

SHAG opposes large-scale redevelopment of the Sutton Hospital site.