The City Property Association has raised some challenges about key issues in London mayor Boris Johnson’s proposed changes to the London Plan.

It has challenged how Johnson will fund the works needed to achieve his 60% carbon reduction target by 2025 which are estimated to cost between £40bn and £80bn.

In its formal response to the London Plan review the CPA said: ‘We are concerned that there is no clear indication of how the required adaptations to existing buildings can be funded. In the current economic climate, it is unlikely that building owner or tenants will be able to raise funds through the normal methods. We are also concerned that any requirement which leads additional costs will act as a further deterrent to new development.

‘We urge the Mayor to use his influence to bring together those who can design and deliver creative solutions to this problem. Without funding - either direct or indirect by way of tax or other fiscal relief - it is unlikely that the objectives will be achievable.’

The CPA also said it did not agree with Johnson that a specific policy relating to tall buildings is required and argues that tall buildings should be dealt with on a site by site basis, otherwise they will be restricted to one or two locations within opportunity areas.

Lastly, on affordable housing the CPA said it welcomed the removal of the 50% mandatory affordable housing target but said that the plan should also refer to viability appraisals in determining the level of affordable housing required on a site by site basis.