One in 10 British holidaymakers have complained about their trip in the past three years, a survey suggests.
But half of those who voiced their problem were left feeling disgruntled about the outcome, the study by Which? Legal Service found.
Some 8% even considered starting legal proceedings in order to get their complaint heard, it was said.
Which? polled 1,449 Britons aged 16 or over who had taken a holiday in the last three years.
One-third of those polled found it difficult to complain, while half said they felt they had been dealt with dismissively by the company or person to whom they complained.
Joanne Lezemore, a solicitor at Which? Legal Service, said there were a range of reasons for the complaints.
"We get people ringing about cruises that haven't stopped at all their locations, which is a major issue for people," she said.
"Then there are people who turn up at their hotel and find half the services advertised aren't there or that it's been advertised as a five star hotel when it's actually only got two stars."
Holidaymakers who were caught up in flight disruption sparked by the volcanic ash cloud earlier this year are still having problems with getting their money back, she added.
The advice given by Which? on how to complain satisfactorily is:
- Raise the problem and the effect it is having on the holiday as soon as possible with the holiday company's representative.
- Explain the problem and give them the opportunity to move them or put things right.
- Obtain a complaint form from the representative, fill it in, get the representative to sign it and keep a copy.
- Take photographs or make notes of the problems in case they need evidence later.
- Write to their holiday company when they get home if the problems are not resolved satisfactorily while they are on holiday.
- Ask for compensation to cover their loss of enjoyment and any other losses.
Which? chief executive Peter Vicary-Smith said: "If you do find yourself in the position of having to make a complaint, then do so as soon as the issue arises, always putting the complaint in writing.
"Don't be fobbed off by your holiday company - a bit of persistence can get you the compensation you deserve."