A London solicitor specialising in child care cases, who asked not to be named, said: "It is causing havoc across the country, and fury. Everyone I've spoken to is very worried indeed.

"A child might be waiting for a decision to be placed in a permanent household or returned to the family. It can take months to get a one day or a two day hearing in family cases."

She said her firm had five cases due to be heard next Tuesday, the day of the funeral, and she had been told they would not now be going ahead. An urgent application that day to give directions for a hearing on May 1 had been postponed till May 20 - after the date fixed for the hearing.

"It's the arrogance of such a decision being made without consultation," she said. "The court system is already under pressure to meet the needs of families. The courts will still be fully manned and the court offices open, but the judges and magistrates will not be working."

The lord chancellor announced this week that the court of appeal, the high court, the crown courts and the county courts would not sit next Tuesday, as a mark of respect for the Queen Mother.

Magistrates courts are locally managed by committees, but the central council of magistrates courts committees recommended that court sittings should be cancelled on the day of the funeral.

Courts will remain open for payment of fines, administrative business, and urgent applications for court orders, such as emergency protection orders and domestic violence injunctions. But flags on court buildings will be flown at half-mast all day.

Liz Goldthorpe, chairman of the Association of Lawyers for Children, said delay was already a serious problem in children's cases. "I'm very surprised it is regarded as appropriate to cause delays in these cases, because it involves having to rebook in a system which doesn't allow a lot of flexibility. It's not a question of a case being rescheduled the following week. This will cause delays of months. I would think that must be unacceptable.

"The average time to get to court in a children's case must be nine to 12 months. Further delays would be anything between two and four months at a guess.

"I wonder what the Queen Mother would have thought. I'm sure she wouldn't have wanted to have decisions about the lives of some of our most vulnerable children delayed as a mark of respect."

A spokesman for the Lord Chancellor's department said the courts would be dealing with urgent business. "In addition, pressing family cases are expected to proceed, subject to judicial discretion."