Grandparents are getting a raw deal under existing family law, according to the latest research.

The report, Beyond the Nuclear: Including the Wider Family, highlights the valuable role grandparents play in families and the legal problems often encountered by people cut off from their grandchildren during marital breakdown or bereavement.

Jointly produced by three UK charities - the Grandparents Association, Family Matters Institute and Families Need Fathers - the report, launched at Westminster yesterday, found that 42% of grandparents lost all face-to-face contact with their grandchildren after parents separated.

Campaign groups are now calling for changes to the law to remove the "unnecessary obstacle" that currently requires grandparents in England and Wales to go to court in order to request permission to make an application for contact rights.

The law north of the border differs slightly, in that grandparents in Scotland can apply for access without first getting permission from the courts, but there is no automatic right to contact - and the Scottish Government has repeatedly insisted it will not amend the legislation to include any legal "presumption" of visitation rights for grandparents.

"Rights are given in relation to children in order to allow a person to fulfil his or her parental responsibilities, not to ensure that person's continuing relationship with the child", said a spokesperson.

However, the Scottish Government compromised with the creation of the Grandparents' Charter in 2006 which sets out the rights of grandparents, but does not make them legally binding.

While in the majority of cases families where parents are separating or divorcing are able to come to their own arrangements without legal action, campaigners argue that the lack of any formal right to access - such as that granted to step-parents - "ignores" the importance of grandparents within the family unit.

Around one million grandchildren are denied any contact with their grandparents, with paternal grandparents disproportionately affected.

Family campaigner and television presenter Gloria Hunniford said yesterday that it was "time for the government to harness the love and attention that grandparents yearn to give to their families", and incorporate it into future policy-making and legislation.

Grandparents have been hailed as a backbone of the British economy in a number of recent studies, including a report by Age Concern that found they saved parents almost £4bn every year on childcare costs.

A survey of 211 people, carried out for yesterday's report, found that before separation 55% of grandparents were directly involved in looking after their grandchildren, while around 1% of children lived full-time with their grandparents.

But with a quarter of the parents of the 12 million children living in the UK expected to divorce or separate, and hundreds more mothers and fathers dying prematurely every year, many grandparents find themselves caught out by the law.

In 2000, Jimmy and Margaret Deuchars, from Glasgow, set up a support group - Grandparents Apart - following their own battle to stay in touch with their granddaughters. When their daughter Susan died of breast cancer 15 years ago, one week after giving birth to her second child, the couple took on the role of caring for their baby granddaughter and her two-year-old sister.

However, when their son-in-law, Joe, found a new girlfriend, things began to change.

"She was from Liverpool, and she just wanted to take the kids away and not have anything more to do with either us or his family," said Jimmy. "But the girls had bonded with me and my wife; they'd stayed with us for three years. We never had any intention of keeping the kids, but it was a terrible blow just to drag them away like that."

The Deuchars eventually reached an agreement out of court. They can now see the girls, who still live in Liverpool, whenever they like.

But Mr Deuchars adds: "Grandparents have no legal rights whatsoever - not in Scotland, England, Ireland or Wales. You have to sue for them.

"We want to see automatic rights for grandparents to see their grandchildren."