Calls have been made for housing reform after new figures show rents in the private sector soared by as much as two-fifths over the past four years.

Tenants in Aberdeen and Aberdeenshire have been hardest hit, with average rents for all properties increasing well above inflation.

The monthly cost of renting a two-bedroom property in these areas rose by 39.8% from 2010 to 2014, official statistics show.

Average rents increased by 17.2% in the Lothian area, 11.1% in Greater Glasgow and 9.8% in Fife over the same period.

In Lothian the cost of one, two and three-bedroom properties was above the rate of inflation while in most other areas average rents changed below the rate.

Across Scotland there was an 11.2% increase in average rents for two-bedroom properties, with rents falling in Ayrshire, Argyll and Bute and West Dunbartonshire.

Graeme Brown, director of Shelter Scotland, said the figures showed the sector was "ripe for reform".

"Scotland's growing ranks of private tenants need rents which are stable, predictable and affordable to make the private rented sector fairer and fit for all," he said.

"The private rented sector plays an increasingly important role in the housing market, which is in a major crisis caused by a chronic shortage of homes."

The charity is calling for 10,000 homes for social rent to be built each year to tackle the problem and reduce pressure on the private sector.

Green MSP Patrick Harvie said: "More and more people find themselves with no other option for housing except private renting, so we must ensure that it is an affordable and secure choice for tenants.

"I want to see a range of measures in the Government's new housing bill to provide relief for private tenants.

"We do need a healthy rented sector and that means supporting responsible landlords too, but there's a very strong case for restricting the frequency and levels of rent increases ."

Labour housing spokeswoman Mary Fee said: "Too many Scots find themselves trapped in the private rented sector, unable to access social housing or get a foot on the property ladder. They need and deserve a system that works for them.

"When the SNP blocked Scottish Labour's fair rent cap they ripped off families across Scotland and sided with landlords instead of Scots facing a cost of living crisis."

John Blackwood, chief executive of the Scottish Association of Landlords, cautioned against any form of rent control.

He said: "These figures show that uniform solutions, such as rent controls as have been proposed by some, would not tackle the underlying problem, would harm investment in the sector in Scotland and make it harder to tackle the current housing crisis."

Responding to the figures, housing minister Margaret Burgess said the Scottish Government was committed to making the private rented sector "an attractive and affordable housing option".

She said: "This is clearly good news for those tenants whose rents have risen at or below the rate of inflation, but a real problem for those affected by larger increases in the hotspot areas.

"Last month I launched the consultation on a new tenancy for the private rented sector, which recognises that rising rents are a problem in some areas and is inviting views on the issue.

"In addition to this we continue to work with the housebuilding industry to deliver more new homes.

"Scottish Government funding for the appointment of Gerry More as Homes for Scotland's private rented sector champion, will drive forward initiatives to boost the supply of new homes purposely built for private rent and will unlock new sources of housing investment."