The average rent in Gwynedd costs nearly a third of the area's median wage, new figures show.
Campaign group Generation Rent said the next government must tackle rent costs by building more homes and stopping landlords from raising rent above wage growth or inflation.
Office for National Statistics figures show Gwynedd’s average rent was £665 a month in May. Separate ONS data shows the median wage for May was £2,092 in Gwynedd – meaning rent accounted for 32% of the monthly income for an average individual.
The figures are based on individual wages – cohabiting couples or those living in house shares will see rent shared between multiple wages.
London saw rent take up the highest proportion of wages. Its average rent of £2,086 accounted for 74% of the median monthly income.
The North East’s average rent of £667 took up 30% of its median pay.
In Wales, the average rent was £736, accounting for 33% of the £2,240 median wage.
Generation Rent chief executive Ben Twomey said: "Prices in shops may have stopped rising so quickly, but renters are still seeing our single biggest cost go up faster than incomes.
"Landlords can raise rent as high as they think they can get away with and use the threat of a no-fault eviction to bully their tenants to accept it.
"We won't fix the cost of renting crisis unless the next government acts to slam the brakes on these runaway rents."
He said more homes are needed alongside protections against unaffordable rent increases.
Rent in Gwynedd has increased 8% from £616 a year ago, and jumped 35% from £494 when records started in 2015.
Shelter chief executive Polly Neate said: "Successive governments have failed to build the social rent homes we desperately need and private rents are continuing to rocket as a result.
"Every day we hear from people who are forced to cough up money they simply don’t have just to keep hold of an overpriced and often shoddy rental.
She said renters are left to accept eyewatering rent hikes" due to competitive rental markets and a lack of protection from evictions, and the next government must urgently ban Section 21 "no-fault" evictions, limit in-tenancy rent increases and extend notice periods.
"But long-term, the only way to take the heat off private renting is to invest in a new generation of genuinely affordable social homes with rents tied to local incomes," she added.