Adults with children are allowed only two alcoholic drinks at JD Wetherspoon pubs in order to limit their stay, the chain has confirmed to the BBC.
JD Wetherspoon has 683 pubs in the UK
A spokesman for the company said it was "uncomfortable" with children being on the premises for long periods because of a lack of play facilities.
But the chain has no plans to display official signage to alert customers.
Instead, refusal will be at the discretion of pub managers, who could even deny parents soft drinks.
The drinks policy came to light when Stephen Gandy contacted the BBC after visiting a Wetherspoon pub in Wallasey on Merseyside for a meal with family and friends.
The group was told that they could not have more than two alcoholic drinks each because they were with a child, even though the child's mother was only drinking water.
Mr Gandy said they were told by the bar's manager that the aim of the restriction was to comply with "child cruelty legislation".
"I tried to tell him that I understand and know the legislation and it's not in relation to cruelty but in relation to comfort, environmental conditions and segregated areas and a comfortable environment for children," Mr Gandy added.
"But he was having none of it and the choice was we could stay but the child would have to go. Obviously we didn't want that so we proceeded to another establishment that made us welcome.
"Imagine a foreign visitor coming in and getting told that - it's unreal."
When the BBC contacted JD Wetherspoon, spokesman Eddie Gershon confirmed the policy was in place, but denied it had anything to do with child cruelty laws.
Mr Gershon said: "Wetherspoons is quite clear it wants children in its pubs but it's not a children's pub in as much as a Wacky Warehouse or that type of place.
"What we don't want is the adult just staying and drinking in the pub while the child is just sitting there and we will 100% back our manager in the approach he has taken."
In relation to Mr Gandy and his friends, Mr Gershon added: "The only people they need to look at are themselves."
Mr Gershon said there were no plans to introduce permanent signs at any of its 683 pubs throughout the UK.
But the company has put guidelines on drinks limits for adults with children on its website.
They read: "Adults accompanied with children wishing to purchase an alcoholic drink should purchase a meal."
"Once the meal has been finished and tables cleared, it is our recommendation that only one more alcoholic drink should be purchased for each adult."
"If parents and their children are visiting our pubs and purchasing non-alcoholic drinks, then there is no limit to the number of drinks that can be purchased or the length of stay."
"In all situations, it is important that our pub managers assess the behaviour and attitude of parents."
"We do not want to restrict families visiting our pubs, in fact, we actively encourage families and have recently won an award for our children's menu."
Mr Gershon said the policy had been received very positively since it first came to light last week.
Nearly 2,400 people have contacted the BBC about the story and many backed the restrictions on time that children can spend in pubs.
But Mr Gandy insisted that Wetherspoons should be more explicit.
"There should be a note on the children's menu informing adults about the policy", he said, "and a customer services telephone number".