Brighton is set to hold what is believed to be the first all-female parliamentary election ever in Britain.

The milestone has been reached after the Liberal Democrats revealed Andrew Falconer, their original candidate for the Brighton Pavilion constituency, had pulled out and would be replaced by one of a shortlist of four women.

Whoever is selected will stand against Labour's Nancy Platts, Green Caroline Lucas and Conservative Charlotte Vere in the next general election, due before June.

Women's equality campaign the Fawcett Society said it was the first constituency anywhere in the country, as far as it was aware, to ever have an all-female contest and described it as a cause for celebration.

Experts from the University of Plymouth, who advise the Electoral Commission on election statistics, said they had no knowledge of any previous occurrences.

Fawcett Society chief executive Ceri Goddard said: "If all the candidates are women that is cause for celebration but also concern that it has taken until 2009, whereas all-male elections are still the norm.

"The voters if Brighton can be pleased that whom ever they elect they will be a step closer to closing the gender gap in parliament where currently less than 20% of our MP’s are women – less than Iraq, Afghanistan and Rwanda.”

The milestone appears to have been reached accidentally. Labour selected Mrs Platts from an all-female shortlist but Dr Lucas was selected by the Greens in a head-to-head with Brighton and Hove City Councillor Keith Taylor and the Conservatives picked Mrs Vere after an open primary between three men and three women.

Mrs Vere was only selected as Tory candidate last month after the party's original selection David Bull stepped down following two years of campaigning.

Statistics show female candidates were the highest vote winners in several wards encompassed by Brighton Pavilion during the last city council election in 2007.

The constituency is expected to be one of the most closely contested in the country. It is held by Labour's retiring MP David Lepper by a 5,000 vote majority but has been targetted by the Conservatives following their national swing and the Greens who have won a string of local and European elections in the city.

The Lib Dems, who finished fourth in the last general election in 2005, said Mr Falconer had withdrawn due to family circumstances in Scotland.

The party will select its final candidate in January. They declined to name those on the shortlist.

Mr Falconer said: "My decision to stand down as Liberal Democrat candidate is boringly pragmatic. Like many local residents I was faced with demands from work and an increasingly challenging and impractical commute. It became clear that because of this I would be unable to commit as much time to the campaign as I would have liked."

It is not yet known whether UKIP or any smaller parties or independents will stand in Brighton Pavilion.