The charity is launching an online survey for tenants who are in the private rented sector to share their experiences of the prices and hidden costs they have been charged.
Current figures show more a quarter of renters in Wales who have used a letting agency have been charged what the charity calls ‘excessive fees.’
It is also says that in some cases tenants have been charged as much as one month’s rent, as well as paying for the bond and rent in advance.
Letting agents argue these charges are in place to cover business and administration costs.
However Shelter Cymru say they should be paid by the businesses themselves or by the landlords who are making a profit.
“These letting agents fees are so unfair on tenants and are causing serious financial hardship when they have to find hundreds of pounds to cover the cost of moving. This makes renting impossible for some people, and finding good quality accommodation in the private rented sector well out of their reach. It’s a very difficult situation for tenants,” said Jennie Bibbings, Shelter CYMRU.