Sutton and Cheam has been identified as one of the key seats in the upcoming general election by the influential parliamentary magazine The House.

The seat has been held by Liberal Democrat MP Paul Burstow since 1997 and had already been flagged by his Conservative rivals as one of the 50 seats it must win if it is to gain a workable majority in the next parliament.

Describing the importance the seat has to the 2015 general election result, The House reported: "Although a Lib Dem seat since 1997, Paul Scully is fighting hard to retake the constituency for the Tories.

"With Emily Brothers, who came out in December as the first transgender PPC selected by a major political party, representing Labour, and local ‘Keep St Helier Hospital’ campaigner Dave Ash making his challenge in the seat of a former health minister, Sutton and Cheam looks set to be a fascinating battleground.

Reacting to the report Mr Burstow said: "It's been a Conservative top 50 target for the past 18 years and all that means is that it is a hotly contested seat.

"It's why the Conservatives are spending a huge amount on letter delivery and direct mail.

"We were told in the run up to the local elections last May that the Conservatives were hoping to take control of the council and the Liberal Democrats increased their majority."

In 2010 Mr Burstow secured the seat with 45.7 per cent of the vote (22,156) , beating Phillipa Stroud on 42.4 (20,548) and Kathy Allen on 7 per cent (3,376) This year Mr Scully will be the fourth Conservative candidate to go up against Mr Burstow.

Mr Scully said: "This election is going to be close and the report shows the significance of Sutton and Cheam to it.

"It shows that when people are casting their vote, as well as looking for a hard working local MP, they will be deciding who runs the country rather than leaving it to Nick Clegg."

The House magazine is edited by the Labour MP Gisela Stuart who wrote that few people are wanting to predict the result of the Thursday May 7 ballot.

She wrote: "In fact, next year’s general election might best be understood as one of 650 odd by-elections.

This guide looks at the 50 most interesting marginal seats - who are the runners and riders and what factors may affect the outcome.

Ms Brothers added: "It's a key seat because this is the most open election in 50 years.

"Its open to Labour, Liberal Democrats and the Tories and possibly UKIP.

"It's a very open constituency."