A row over basement developments has broken out after plans to build a centre said to provide cutting edge of cancer treatment was approved.

Westminster City Council has given the green light for the redevelopment of 141 and 143 Harley Street as well as 28 and 29 Devonshire Mews West, in Marylebone , which will enable the installation of a proton beam therapy facility.

The local authority’s Labour group says the Marylebone planning permission will see a triple basement development, and comes despite the Conservative administration’s new policy which restricts basements to just one level .

Last month the council set up a Sub Squad to help people whose lives are affected by noise, dust and traffic caused by basement developments .

Some 17 people living in the mews objected to the proposals, but the council’s deputy leader and cabinet member for the built environment moved to calm concerns.

Cllr Robert Davis MBE, said: “We’re committed to ensuring that Westminster has world class healthcare and remains a centre for the development of life-saving technology."

“I can think of few better reasons to approve a development than creating a centre of excellence where people receive high quality medical care and attention, particularly for the treatment of an illness that affects so many of us," Cllr Davis added.

“Our new Code of Construction practice and a number of additional conditions put in place after granting planning consent will mitigate the impact of this development on the local community.”

Some are still unhappy, however.

The Labour group quotes one resident as saying: “I really feel that the council’s own policy on basements, in particular so soon after its adoption, would be jeopardised were an exception be made and this development be permitted.

'Totally ill-suited for this quiet residential cul-de-sac mews'

"I have no doubt you will appreciate, that although this project may serve a worthy medical cause, it is totally ill-suited for this quiet residential cul-de-sac mews.

“More fundamentally, were this project to get consent, it would just make the promises of the council to protect the residents through its new policy on basements just sound extremely hollow.”

Cllr Paul Dimoldenberg, the Labour environment spokesman, said: “It is extremely disappointing that the council’s new basements policy, which has cross-party support, should be breached so soon by this triple 'super basement’ that is totally unsuited to a quiet cul-de-sac mews."

“Surely, a more appropriate commercial location, away from residents, would have been more appropriate for the years of construction, disruption, noise and dust that are involved in digging a triple basement?," Cllr Dimoldenberg said.

“Many residents in Marylebone, St John’s Wood, Bayswater and Pimlico will now be asking if their street is next for a Westminster Council-approved triple basement?”

The ruling comes after the council revealed it had received around 150 applications for basement developments in each of the last five years.