With about 250 friends on Facebook, Paul Cookson did not expect a "rant" he posted to have much impact.
He wrote that he was "sick to death" of being "ripped off" by companies which put up holiday prices outside school term time.
A few friends agreed, and followed his request to "share this post if you have also had enough".
It soon went viral, and more than 143,000 people have shared it so far.
Supporters also began signing an online petition calling for government action and this has now gone far beyond the 100,000 signatures needed for a possible debate in Parliament.
Mr Cookson's initial post, entitled "school holiday rant", asked why parents should be "penalised" for doing the right thing and not taking their children away during term time. It came about after he tried to book a holiday with his daughter.
He told the BBC he was stunned by the response on Facebook, with many people encouraging him to "carry it on and fight".
So the 41-year-old set up a Facebook group called Holiday Price Increase, in which many people have shared examples of price changes.
One of the group's members posted a link to the e-petition, which is entitled: "Stop holiday companies charging extra in school holidays".
Mr Cookson, who lives in Chillington, south Devon, said the petition had about 3,000 signatures when it was first posted on his group.
"I thought it was exactly what I would've started, so thought I may as well help it along," he said.
Mother-of-two Donna Thresher, from Essex, set up the petition in March 2013 after being "outraged" at the £600 difference in the cost of taking her family away for a weekend during the holidays.
She thought the petition - which calls for a "cap" on percentage price rises in the school holidays - was "dead in the water" until Mr Cookson's Facebook post ignited interest in it.
Campaigns which reach 100,000 signatures on the government's e-petitions website can be considered by the Backbench Business Committee for parliamentary time - though this petition has not yet been considered.
Mr Cookson said the petition's call for price regulation might not be successful but it was raising awareness and increasing the chance that holiday providers would change their policies.
"The ideal is to work with the holiday companies directly to advise them on the business of reduced-priced holidays in these set times - it can be done," he said.
Earlier this month, a Shropshire couple who took their children on a week-long holiday during term time were ordered to pay £1,000 in costs and fines by magistrates.
New rules which came into force in September mean head teachers can only grant absence outside school holidays in "exceptional circumstances".
Defending the new rules, the Department for Education (DfE) said children who missed school lost out on "valuable learning time".
Almost 200,000 people have signed another petition on the 38 Degrees Campaigns by You website calling for the rule change to be reversed.
In a 2012 poll of 2,000 parents by LV travel insurance, 55% admitted they had taken their children on holiday during term time.
The Association of British Travel Agents (ABTA) said prices were "an issue of supply and demand".
But it said a "potential solution" would be "staggering" holiday dates, rather than having most schools off at the same time. Such a system is already used in Germany, it said.
Virgin Holidays said its view on the issue was "broadly in line" with ABTA's.
The DfE said academies and free schools already had the power to set term dates and council-run schools would get that power from 2015.
"We want schools to consider changes to term times that will benefit pupils' education and work for their families," a spokeswoman said.
But last year the National Union of Teachers warned letting schools set different term dates would cause "chaos" for families booking holidays and would allow holiday companies to extend their premium rate periods.
The Department for Business, Innovation and Skills said the UK holiday industry was an "extremely competitive market" which relied on profits from "peak periods".
A spokeswoman added that any suggestion of "anti-competitive" behaviour should be reported to the Civil Aviation Authority or the Office of Fair Trading.
Center Parcs, the subject of Mr Cookson's original "rant", said its prices were based on supply and demand.
"We reduce our prices significantly during off-peak periods to reflect the lower demand at these times," it said, adding that it reinvested "millions of pounds each year" into its holiday villages.