Struggling parents say they are "devastated" that a charity they rely on is to close due to lack of funding.

Parentline Plus, based at The Park centre in Daventry Road, Knowle West, is a local branch of a national charity but is set to wind up at the end of April after the loss of £50,000 a year in funding grants from the national Parenting Fund.

The service helps about 500 local parents and grandparents each year who are struggling to cope with behaviourally challenged children; those facing having their children taken into care because of drug or alcohol problems; and grandparents who have become the main carers for their grandchildren.

Volunteers and users of the organisation are devastated. They say its services are vital in keeping families together in times of difficulty and also in helping parents with drug and alcohol problems on the road to recovery by offering them hope and helping them improve the relationships they have with their children.

Shirley Andrews, 53, of Knowle Park, is a volunteer at Parentline Plus and runs courses in understanding children's behaviour and anger management. She has written to Bristol South MP and Health Minister Dawn Primarolo and now plans to appeal to the city council for rescue funding.

Shirley was introduced to Parentline Plus when she was going through big changes in her life after she took over full-time care of her four grandchildren.

She was working full-time as a retail manager, looking after the children and her home, while dealing with her partner leaving because he couldn't cope with the change in lifestyle.

Shirley said: "This is parents supporting parents. It's our motto, and I always tell people that instructions aren't included when you have children. Every parent struggles at one time or another and no parent is perfect.

"There was a time when I couldn't even leave my house because I was so low and I got through that with the support of Parentline Plus. When I was asked to do volunteering and run some courses I knew this is where I had to be – supporting others who had been through difficulties.

"We offer so many services, including counselling, outreach programmes, classes and courses, as well as referral to other organisations. We also work in many communities, from Filton to Easton over to Knowle. I, along with many other people, will be devastated if this service goes and the community will be worse off for it."

The charity has 10 centres across the country and five of those – Bristol, Merseyside, Hampshire, Croydon and Nottingham – applied, but failed to win, any of this year's Parenting Fund money.

Parentline Plus's Newcastle centre is the only centre to have been awarded the funding.

Parentline Plus chief executive Jeremy Todd said: "Like many organisations in the current climate, we are experiencing severe funding cuts and this is sad news for our hard-working staff and volunteers, and for the parents we support.

"Inevitably this will have some knock-on effect on our ability to provide the important services we do on a local level.

"I would like to stress that this will in no way impact on our national support services to help parents and carers of children, including our 24-hour, free and confidential Parentline, 0808 800 2222, and we will be working hard to continue to be there for parents. Parentline Plus is working with staff and volunteers to support them through this difficult time and the charity's board of trustees is due to meet this week to discuss this issue."

The Parenting Fund is administered by the Family and Parenting Institute on behalf of the Department for Children, Schools and Families. No one from the department was available for comment on the funding decision on Thursday.