Acevo chief executive Stephen Bubb has written an open letter to Conservative leader David Cameron warning that the recommendations for the third sector contained in the Social Justice Policy Group’s report Breakdown Britain must be backed up by extra investment.

“The report contains a number of significant proposals for the development of the role of the sector and many of these are in themselves welcome. However these proposals should not be funded through taking resources which are already assigned to the sector,” the letter said.

“An increased role for the third sector in delivering public services and tackling poverty must come with investment to overcome the barriers which prevent us developing our role,” it warned.

Bubb told Cameron that Acevo members wanted to see an increase in the total pot spent on the most socially excluded and vulnerable in society. “The sector cannot deliver effective public services in the context of cuts to public spending,” his letter said.

“I would ask you to carefully consider these proposals and urge you to tackle poverty through the role of the third sector, not through tax breaks for many of the less marginalised in our society.”

The Conservative Party has yet to make an official response to the letter.