LISBON, April 4 (Xinhua) -- Lisbon and Porto have a higher ratio of tourists to residents than renowned tourist spots Barcelona and Prague, the Institute for Tourism Planning and Development (IPDT) revealed on Wednesday.

The IPDT used statistics that measure arrivals and average lengths of stay in order to calculate how many tourists are in a city at a given moment. The results were published in the Jornal de Noticias newspaper.

Lisbon averages 4.5 million tourists per year, meaning that for every resident there are typically 9 tourists.

Porto welcomes 1.6 million tourists annually, the equivalent of 8 visitors per local.

The ratio is even higher in Albufeira in the Algarve region on Portugal's south coast, where tourists outnumber locals by 39 to 1.

But Albufeira is a tourist resort and the aim of the study was to show tourist pressure on multi-sector towns.

Barcelona, in Spain, and Prague, in the Czech Republic, therefore offer better barometers, as they enjoy reputations for excessive tourism. Both average 5 tourists per resident, almost half that of Lisbon and Porto.

However, sector specialists gathered in Vila Nova de Gaia, near Porto, for the 13th International Tourism Forum, denied there was a problem.

"We should focus on the positive effects," said Luis Araujo, president of Tourism Portugal, "such as urban revitalization and job creation."

However, Araujo also recognized that "growth must be spread around the whole country." He suggested more cycling, walking and touring packages to take tourists out of Portugal's two major cities and into more remote, rural areas.

Portugal is experiencing a tourism boom that boosts the economy, but also forces up rents for locals and puts added strains on municipal services.

Lisbon and Porto have introduced tourist taxes to help cope with increased pressures. The Algarve region voted to follow suit in March.

Sintra, a popular tourist destination near Lisbon, announced on Wednesday that it was also to introduce such a scheme. A 2 euro per room charge will be applied to anyone staying overnight from next year.