Sellers are attempting to cash in on a buoyant housing market by raising average asking prices in some London boroughs by more than 7% in a month, according to property website Rightmove.

Across the country average asking prices rose 2.6% in April, and were 7.3% higher than this time last year – the biggest annual rise since October 2007, before the credit crunch took hold, according to the website's monthly figures.

In the north London borough of Brent, where lender Nationwide recently reported that sale prices had risen by almost a third over the past year, Rightmove said new asking prices have increased by 7.9% in a month. In neighbouring Camden, asking prices have risen by 7.5% since mid-March, and in nearby Harringey they are up by 7.1%.

The website also reported a strong ripple effect pushing asking prices to new highs across the south of the country.

Economic forecasters at Ernst & Young meanwhile have predicted house prices of 7% nationally this year will be repeated in 2015, but discounted fears of the housing market heading for a bubble.

Arguing that a revival in house building and tighter lending criteria would keep a lid on prices outside London, the E&Y Item Club predicted UK house price rises would moderate to 4.2% in 2016.

Peter Spencer, chief economic adviser to Item, said: "The housing market is not experiencing a typical debt-fuelled recovery. Gross mortgage lending has increased but this has largely been financed by an increase in repayments by existing borrowers.

"New mortgage lending remains at rock bottom while government initiatives such as the Help to Buy schemes will be having little impact on prices in London, where activity is fuelled by cash rather than mortgage borrowing."

The Rightmove figures showed that in Greater London, sellers are asking 15.9% more for homes than they were last April – at an average of more than £572,000 – and asking prices in and around the capital are now 41% higher than in 2007 – a rise of more than £168,000 on the average property.

But in the north and in Wales sellers are still expecting less: in the north-west of England, asking prices remain 8.8% less than their 2007 peak, despite a 2% year-on-year increase, while in Wales and Yorkshire they are still more than 7% below previous highs.

Latest figures from rival website Zoopla showed that 27% of properties on sale in March had been reduced in price, and that the average discount stood at 6.25%, or £20,782.

In Wakefield 42% of properties on the market had seen price cuts, and even in London, where activity levels have been high, 15% of asking prices had been reduced.

However, in the hottest parts of the market, estate agents are reporting frenzied bidding by would-be buyers, with some properties attracting multiple bids over the asking price.

Rightmove's director, Miles Shipside, said: "Supply in much of the south is ridiculously tight, with for sale board blackspots in many popular locations within easy commuting distance of London," he said. "There are vicious circles where there is so little property for sale that few local home-owners are willing to come to market to trade up, exacerbating the shortages and boosting sellers' pricing power."

The monthly figures are compiled using the asking prices of properties which are newly listed with estate agents, and do not reflect the prices achieved by sellers.

However, Shipside said he did not expect changes to rules around mortgage lending which are due to come into force this month to calm the market. The rules, which will force banks and building societies to undertake tougher affordability checks before they grant loans, may reduce some borrowers' buying power, but Shipside said the imbalance between supply and demand was likely to support prices.

"Whilst a higher percentage of borderline mortgage applications will be weeded out, the overall numbers of those who are mortgage-worthy and wish to borrow and buy, combined with lenders who are flushed with funds, is still likely to result in increased buyer demand," he said. "It is encouraging that more home-owners are selling, increasing churn and supply and helping to moderate house price growth. However, because we should have built more in the past and are still not planning to build enough, prices will continue to rise in popular locations, further stretching affordability."