Conservative party officials are to hold an American-style "open primary" to select the person they want to be the next MP for Tonbridge and Malling.

The decision means anyone who lives in the constituency and is over 18 will have the chance to vote on the candidates shortlisted by the association - even if they do not belong to the party.

It is the first time such a process, modelled on a system routinely used in America, will have been used to select a Conservative candidate in Kent.

The selection process for a successor to Sir John Stanley, who is to step down in 2015, was agreed by the constituency association on Wednesday.

As many as 300 potential applicants are expected to bid to become the candidate for what is one of the safest Conservative-held seats not just in Kent but the country.

There has been speculation that Boris Johnson, Mayor of London, could be interested in throwing his hat in the ring but that now seems highly unlikely.

Sir John secured a majority of more than 18,000 at the election in 2010, taking more than 50% of the vote.

Among those known to have applied is Craig Mackinlay, who was the Conservative candidate in the Kent crime commissioner election last year.

The final selection meeting will be held in November after the association has drawn up a final shortlist of four candidates.

Anyone on the electoral roll in the constituency will be able to attend that meeting and vote.

Jacques Arnold, the chairman of the association, said: “We decided to go down this path because these days, fewer people belong to constituency associations and we wanted it to be open to as many Conservative voters as possible.

"The reality for all parties these days is that people do not want the commitment of belonging to an association.”

At the 2010 general election, the Conservatives used an open primary process to select a candidate for Totnes in Devon. That candidate was Sarah Woolaston, who became MP.

The idea of using primaries has been advocated by the coalition as a way of involving and engaging ordinary people in politics.

David Cameron had said the party would look to adopt the process in 200 safe seats.

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