The net we use in order to catch and support children and families in distress is being stretched far too tightly

ADSS President, Moira Gibb

It said unqualified and inexperienced staff were being used in the frontline.

The warning comes two days before a public inquiry begins into the circumstances surrounding the death of eight-year-old Victoria Climbie, from north London.

The involvement of social services, the police and the National Health Service failed to prevent the tragedy.

Stark warning

The Association of Directors of Social Services issued the stark warning on Monday that mistakes may be made by staff under immense pressure, as it revealed the findings of a survey of its members.

An inquiry into Victoria Climbie's death begins this week

Its president Moira Gibb said that there were 30,000 children on the child protection register and 50,000 cases that social services were working with where there were child protection concerns.

"The net we use in order to catch and support children and families in distress is being stretched far too tightly.

"There is a very real danger of some of them falling through."

The survey of social services departments in England by 78 authorities found that there was a 14.7% vacancy rate of social worker posts in July.

This is equivalent to over 2,000 unfilled posts.

Mrs Gibb said: "That's a big chunk out of our service.

"Those who are there are having to work harder in more difficult circumstances.

"And the risk is that under that pressure they will make mistakes."

The survey also found that some authorities are concerned that long-serving, experienced staff are being replaced by unqualified or newly qualified social workers and that authorities have been forced to recruit staff from as far afield as South Africa and Australia.

Climbie inquiry

The figures were revealed at briefing ahead of Lord Laming's inquiry into the circumstances surrounding the death of Victoria Climbie.

The youngster died of neglect while under the care of her aunt and her partner, despite the involvement of social services, police and the NHS.

Marie Therese Kouao, Victoria's aunt, and Carl Manning, Kouao's boyfriend, were jailed for life in January for the murder of the girl in Tottenham, north London, in February last year.

The child had 128 separate injuries on her body and died from multiple organ failure, malnutrition and neglect.

But Mrs Gibb said: "Throughout the long months of the inquiry, social workers will continue to be protecting children, and young children will continue to need protection".