Letting agents must display in any advertising or publicity material the compulsory fees to be paid by consumers planning to rent a property, the UK's advertising watchdog has said.

The tough message from the Advertising Standards Authority (ASA) comes as it publishes a ruling against estate agent Your Move for an advert that appeared on property website Rightmove.

Your Move broke advertising rules by not making clear that non-optional fees and charges – in this case an administration fee – would be added to the quoted price.

The ASA said that although the law had not been changed, advertisers would now have to make clear in the quoted rental price if there were compulsory fees and charges.

If the fees cannot be calculated in advance because of, for example, an individual's circumstances, then the advertiser must make clear that additional fees and charges have been excluded and provide enough information for the consumer to establish how they will be calculated.

Guy Parker, ASA chief executive, said: "Hidden fees are not only unfair, they hit those who are struggling hardest. Our ruling today makes clear that letting agents need to get their houses in order and treat potential tenants fairly."

Young people and students were particularly vulnerable, he said. "It is now our priority to make sure agents across the sector bring their advertising into line."

Your Move said in a statement: "We strongly believe in the principles of the Consumer Protection from Unfair Trading Regulations 2008, as demonstrated by the fact that we provide applicants with information at a stage prior to them making their decision to enter into a tenancy agreement – the timing of which compliments the Office of Fair Trading guidance for estate agents, and that we have also actively engaged with the regulators, in particular the OFT.

"In view of the findings, however, we will of course be reviewing our approach, and in support of this look forward to the OFT introducing official guidance for the lettings market as soon as possible to ensure greater clarity on matters of this kind."

Last month the OFT urged the government to consider new laws for lettings agents to improve the rights of tenants and landlords, alongside a call for lettings agents to be forced to provide a full tariff of charges before a tenant signs a contract.

The number of renters has risen in recent years, as high house prices and stricter mortgage lending criteria have made it increasingly hard to get on the property ladder – in 2010/11 3.6 million households in England were renting, up 2 million on 1999's figure. According to the Council of Mortgage Lenders, 2012 saw the number of buy-to-let loans taken out jump by a fifth.