When the Victorian Taxi Association launched a campaign on Monday calling for people to give honest feedback about its service, chief executive David Samuel said he expected criticism.

He was right. Using the official name of the campaign, #YourTaxis, people have taken to Twitter to share their experiences riding in taxis throughout the state.

The responses have been scathing; some people shared disturbing experiences of being sexually harassed or verbally abused by their driver.

Others said drivers had refused to take them on short trips, and one person said the driver had fallen asleep.

As part of the “Your Taxis” campaign blitz, the association is encouraging people to share feedback on the campaign website, and is offering a prize of free taxi rides for one year. Although the association has encouraged people to share taxi stories on Twitter using the hashtag #FirstCabOffTheRank, people hijacked the name of the campaign, #YourTaxis, to share their stories instead.

But on Tuesday Samuel said the campaign had not been a failure.

“At the end of the day we expected criticism, and we are not trying to sell something here,” he told Guardian Australia.

“We wanted to create a forum where people can share their views, good and bad, and we’ll be responding to all of those so long as they are reasonable.

“The notion that our campaign has failed in some respect because of this feedback is something we reject. It is vital we get this feedback and get things right if we want to change.”

Samuel said taxis provided a vital service, including transporting people living with disabilities. It was important that those people in particular felt safe using Victorian taxi services.

But he admitted he found some of the feedback to the campaign concerning, particularly complaints from customers who said they had been abused.

“Anything that involves people being physically, sexually or verbally abused, harassed or intimidated is completely unacceptable,” Samuel said.

“Those concerns extend beyond this campaign and are always sent to our regulator and must be dealt with. Any driver found to have committed offences will be dealt with seriously.”