Churches are being invited to pray for their parent and toddler groups on 2 June.
The National Day of Prayer for Parent and Toddler Groups is being coordinated by 1277, an alliance of churches and agencies supporting the work of church-based toddler groups.
Many churches run parent and toddler groups as a way of reaching out to their local communities.
"For many young children and their parents, the parent and toddler group is a highlight as they meet up with friends to play and chat, but for many it is also the only time they will come into contact with a local church community," said Alison Clark, chair of 1277 and children's evangelist with Praise and Play.
"It's a fantastic opportunity for the church to serve their community and share the gospel at the same time."
An estimated 27,000 churches are running parent and toddler groups, serving millions of children and their carers.
Many of the groups are made possible thanks to volunteers who donate their time to set up church halls, organise craft activities, and building relationships with the children and parents.
The day of prayer has been timed to coincide with National Family week and churches that don't yet have a parent and toddler group are being encouraged to use the day of prayer as an opportunity to pray about whether they should start one.
Ian Bunce, Faith and Society Networker for the Baptist Union and a member of the 1277 network, said: "With toddler groups reaching 52% of the toddlers and carers in this nation, it has the greatest potential of any mission activity of the church.
"The frontline missionaries, that are the volunteers, need our prayers that they can be free samples of Jesus week by week. Imagine the possibilities if the whole church really supported this ministry."
Resources for the day are available at http://www.1277.org.uk