The sector chief executives body wrote to the three main political parties two weeks ago asking them to spell out their positions on the scheme, which has created 70,000 jobs in the voluntary sector.
Peter Kyle, deputy chief executive of Acevo, said the Conservative Party's silence on its plans for the fund had prompted concerns that they might regard it as an easy target for immediate cuts.
But Theresa May, shadow work and pensions secretary, wrote to Acevo on Wednesday saying her party had "no plans to change existing Future Jobs Fund commitments".
Nevertheless, May did not commit to extending the scheme after funding expires in March 2011. She said the Tories would review the fund to see whether it delivered "long-term sustainable work".
The fund pays employers to hire young people on at least the minimum wage for six months.