Health services in Wandsworth could receive £45m less next year following an overhaul of the NHS funding allocation system.

NHS England’s latest funding formula has shown the borough’s clinical commissioning group (CCG) to be overfunded annually by £45m and as a result the money will be withdrawn and redistributed in the 2014-15 financial year.

Wandsworth CCG received £391m for 2013-14, based on a 40-year-old formula, but fresh calculations by NHS England, taking in data from the 2011 census, showed the correct amount of funding should have been £346m.

The shortfall, almost 11 per cent, is the fourth highest in London.

Many other London health authorities including Bromley, Croydon and Hounslow, who have traditionally been underfunded, are now due to receive considerably more money.

The news of Wandsworth's shortfall will surprise many because, in recent years, the borough's health bosses have managed its accounts prudently resulting in a budget surplus of £12m in 2012-13.

Conversely Croydon was outed just two years ago as having a budget deficit of more than £20m yet despite the poor management of its accounts, it is due to receive an extra £31m next year.

Dr Mike Squires, from campaign group Keep NHS Public, said: “Forty-five million pounds is a huge amount of money and represents about 10 per cent of the entire budget.

“It does seem Wandsworth will be paying out a lot and will no doubt have to do more with less, just like every other public body in the country.

“It will be interesting to see whether this formula goes ahead and how the CCG plan to manage the outcome.”

The new funding formula is largely based on population. Croydon’s allocation rose by so much because its residents increased in number by 30,000 to 363,000.

But, according to the same census data, Wandsworth’s population rose by 13 per cent, from 270,000-307,000, between 2001-2011 yet it will receive £76m less than Croydon.

A spokesman for Wandsworth CCG said the formula was still not approved and a final decision would be made in December.

He said: “The £45m figure is taken from one proposed formula. It is part of an ongoing review and nothing is as yet finalised.

“We are working hard and doing everything we can to make sure it works for the people of Wandsworth.”

CCGs were introduced to replace primary care trusts after the passing of the Health and Social Care Act 2012, following a comprehensive review of NHS England’s funding allocation policy.

The aim was to give GPs and other clinicians the power to influence commissioning decisions for their patients.

NHS England said CCGs were still being consulted over the proposals and confirmed no decision would be made until later in the year .

A spokesman said: “NHS England has a legal duty to ensure that patients have equal access to services across the country and to address health inequalities.

“It is only right that we examine the risks and benefits of a range of potential options for the future approach to allocation of funds.

“We are currently seeking the views of CCGs. Any decisions will take into account how a change in funding allocation will be introduced, and over what time period, to ensure there are no adverse effects on local services.”