A new rule aimed at cutting the number of expert witnesses called in family cases has come into force this month.

Previously, evidence from experts such as psychologists and doctors would be heard if it was ‘reasonably required’. Since 1 February judges have begun applying a tougher test, allowing evidence only if it is ‘necessary’.

In reaching a decision on whether to grant permission, the court must have regard to factors including the cost and impact on the court timetable, whether the evidence could be obtained from another source, the issues to be addressed by the expert and the questions to be put to them.

In children’s proceedings, the same test applies to permission to instruct an expert and for a child to be examined for the purpose of providing expert evidence.

The changes stem from the recommendations of the family justice review chaired by David Norgrove, which reported in November 2011, and fit with proposals on the modernisation of family justice published by Mr Justice Ryder, and endorsed by the lord chief justice last summer.

The president of the Family Division Sir James Munby said: ‘There is no question of families being denied the chance to call evidence they need to support their case or being denied a fair hearing. But the new test gives judges more control over expert evidence in family proceedings.

‘The rule change gives family judges the means to make robust case management decisions to make sure the expert evidence is focused and relevant.’

Munby said that the change underlines the key role of the court in determining what expert evidence it requires to help it reach decisions, and is a ‘vital component’ of the active judicial case management that will be needed to prepare the ground for the new single family court, which due to come into being in April 2014.

Denise Lester, chair of the Law Society's children committee, said the change has come in the context, in the public law arena, of having to deal with cases in 26 weeks.

She said: ‘It has yet to be determined what is "necessary" and it's fair to anticipate case law in this area.’ She suggested the change may pose problems for litigants in person who will not be expert in identifying issues and therefore would not be able to focus on what is necessary.

‘Operationally, judges might find it a handful when dealing with litigants in person,’ she said.

The Law Society has published a practice note and developed a suite of templates to help solicitors who instruct experts in family and children court proceedings.