THE Conservatives are today handed the tantalising prospect of snatching Tony Blair's old seat of Sedgefield, as part a dramatic rewriting of Britain's electoral map.

An election expert predicted the new-look Sedgefield and Yarm seat - taking in chunks of the current Stockton South seat, including Eaglescliffe and Ingleby, as well as Yarm - could by claimed by the Tories at the next election.

Click here to view a map showing the proposed new constituencies

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Meanwhile, the redrawn Darlington and Middlesbrough South and Guisborough seats were also predicted to be winnable for the Conservatives, in what promised to be a revival in the south of the region.

The verdict will spark fresh controversy over the changes, which will cull 50 UK seats by 2015 - to end what the Conservatives believe is a strong Labour bias in the current set-up.

Last night, one Labour MP said the trend would be echoed across Britain, creating more marginal seats where the party would need to win over non-Labour voters in order to seize back power.

Jenny Chapman - while insisting her own Darlington seat would remain Labour - said: "We will need to appeal to white van man and people who want to set up a free school, for example.

"We will need to be less focused on our core vote and more on the centre-ground of politics. This could result in a very different Labour party."

The threat to Labour was emphasised by Lewis Baston, of the research group Democratic Audit, who said: "There could be Conservative MP for Sedgefield at the next election - which I'm sure the party would like very much.

"And when you look at the proposed changes to the Darlington seat, it is realistic for them to hope to take both seats, if they do well at the next election."

In the North-East, three of the 29 seats will disappear, one in the south of the region and two in Tyne and Wear, where Blaydon and North Tyneside will go. No constituency will be untouched.

North Yorkshire retains eight constituencies, but they are redrawn so that chunks of Foreign Secretary William Hague's Richmond seat go into a new Malton constituency - with other parts of the current Thirsk and Malton seat gained.

All the region's new constituencies will have between 72,810 and 80,473 voters, requiring them to cross council and natural boundaries to achieve near-equal size.

The Boundary Commission said the current Darlington seat was large enough to survive the shake-up, but the other changes made it necessary to bring in two Tory-inclined wards, from Sedgefield.

Ms Chapman said the inclusion of the Heighington and Coniscliffe and Hurworth wards made sense because of school catchment areas, adding: "I'm happy with it."

As well as four solely County Durham seats, a further one - the proposed Consett and Barnard Castle constituency - would take in two wards in Northumberland.

A significantly altered Bishop Auckland constituency includes the towns of Crook and Spennymoor, while North Durham is renamed Chester-le-Street, to include the Burnopfield and Dipton ward from the existing North West Durham constituency.

The new Durham constituency includes Ferryhill and Trimdon wards, but no longer extends west of Brandon. Easington is largely unchanged, but with the inclusion of Thornley and Wingate wards, from Sedgefield.

A new Stockton and Billingham seat allows almost all of the town of Stockton-on-Tees to be included in a single constituency. Thornaby-on-Tees is included in the proposed Middlesbrough constituency.

Middlesbrough South and East Cleveland would be renamed Middlesbrough South and Guisborough, to include Normanby,Ormesby, and St Germain's wards.

Last night, James Wharton, the Conservative MP for Stockton South, declined to reveal his own future plans, but said: "These are substantial changes to the map. There are lots of marginal seats.

"But the important aspect is the principle that we should have fewer seats in constituencies of equal size."

But Ed Miliband, the Labour leader, accused the Conservatives of "gerrymandering" the electoral system, although the party said it would "engage constructively" with the commission's consultation process.

The shake-up has already triggered furious protests from many Labour MPs, who have warned that tens of thousands of unregistered "ghost" voters are not being counted.

But it must first be voted through parliament in 2013, in what is likely to be another Coalition flashpoint, dividing the Conservatives and the Liberal Democrats.

What do you think of the changes? Do Barnard Castle, Consett and Haltwhistle fit together? What about Sedgefield and Yarm? We want to hear from you - have your say below.