TONY Blair is sitting on a £300,000 nest egg thanks to property price rises in the North-East.

The Prime Minister's constituency home, Myrobella, in Trimdon Colliery, County Durham could now be worth up to £400,000, making it his best property investment to date.

His agent John Burton said he thought the Blair's had paid about £30,000 for the four-bedroom Victorian house in 1983, which is named after the Myrobella plum trees that are in the garden.

"It needed completely doing out though, so it would have cost probably nearer £60,000 in the end," said Mr Burton.

"There were two sisters living there before and they had sort of split it into two houses inside, so it all needed doing."

However, despite the hefty profit the Blair's could make on the property, Mr Burton does not believe Myrobella will go on the market any time soon.

"He loves Myrobella, and I am sure he will keep it on in six years time when he packs in. He likes the area, he loves Trimdon and Sedgefield and has made a lot of friends there, so I'm sure they will keep it."

The profit made on his constituency home is in contrast to the Blair's latest purchase in London. They are reported to have paid £3.6m for a house in the exclusive Connaught Square, near Hyde Park - making it the most expensive in the square.

The five-bedroom house is already understood to have been let at an estimated £150,000 a year.

The purchase is said to continue the Blair's poor timing in the property market, as the couple seem to manage to sell when the market is rising and buy as the market falls.

The Blair's sold their home in Richmond Crescent for £615,000 soon after the 1997 General Election.

They made a profit on the Islington house, but missed the subsequent London boom. The house would now be worth £1.5m.

Cherie Blair's controversial purchase of two flats in an affluent area of Bristol for £270,000 each in 2002, continued the trend.

She bought at a time when the buy-to-let market had become swamped and had started to falter.

Figures from Nationwide show house prices have risen on average by 19 per cent, but in the North-East they rose more than 40 per cent in the past year alone.