The charity, along with HCL Social Care, surveyed 487 children's social workers for its Voices From The Frontline report, half of which had more than 10 years' experience.
This found that a fifth of respondents were not aware of the act placing a 26-week time limit on care proceedings.
A lack of information sharing about policy changes from senior managers was cited as one of the reasons for the knowledge gap, with half saying there are not consulted by management on policy or practice decisions.
The VCF said the findings highlight how difficult some areas will find it to meet the 26-week care proceedings targets.
Its chief executive Mor Dioum said: “We welcome the Children and Families Act, which encourages development of the childcare sector, as well as ensuring a strong advocate for children’s rights.
"However, we are concerned that, despite a raft of reviews and recommendations over the past five years, the current social work system is not significantly robust enough to deliver on the act. We now have evidence from the frontline that this is the case. "
The survey also showed that social workers felt overworked and poorly supported by management. Just 15 per cent said they felt adequately supported by their managers and only 21 per cent said they felt optimistic about their futures in social work.
When asked what was needed to improve the profession the strongest request was for additional resources to reduce caseloads, followed by more staff, cuts in red tape and better management supervision.
Dioum added: “We have observed, with growing alarm, the significant budget cuts levied on local government, which has consequently compressed the strain on the children and families’ social work sector.”
The College of Social Work chair Jo Cleary added: “The report rightly draws attention to the importance of effectively engaging practitioners in the reform agenda, building professional system leadership and ownership of high standards.”