The Prime Minister said this was because the Hindu Murugan shrine in Batu Caves, "is a revered and respected site" among the Hindu community worldwide.
He said this assurance would be part of efforts to protect the site, adding that the Batu Caves temple complex should be preserved to protect it against elements that could threaten it.
"I give you my assurance that if Barisan Nasional takes over Selangor, we will cancel this project," he said.
"We do not want development in the surrounding area to pose a threat to this place," he said at a Deepavali open house organised by the ethnic Indian political party, Malaysian Indian Congress (MIC).
Najib said Barisan was a government that would keep its word and fulfil its promises.
It was reported that Batu Caves would face the risk of caving in if a condominium project, located 120 metres away from the iconic Lord Murugan statue, was to proceed.
The statue, made by Indian artisans, is the largest Murugan statue in the world.
The proposed serviced residences project was temporarily stopped following orders from the state government to conduct soil testing.
MIC president G Palanivel said the Indian community welcomed the Prime Minister's pledge.
Palanivel, who is Minister in the Prime Minister's Department, said the Selangor Government should immediately cancel the project, which apparently would endanger the fragile nature of the limestone hills.
Najib also said the iconic complex was set to gain global recognition.
"The significance of Batu Caves was discussed by the Cabinet and it was decided that the Information, Communications and Culture Ministry will submit an application to UNESCO for it to be consider as a World Heritage Site (WHS)," Najib said.
Located at a 400 million-year-old limestone hill, Batu Caves is home to a series of caves and the famed 272-step Hindu temple dedicated to Lord Murugan.
