The chairman of the Hands Off the Conquest Campaign, who fought for two consultant-led maternity units in the Hastings and Eastbourne, made her application to the LibDems following the recent PCT decision to back a one-site option for maternity services.

Speaking about her decision, Margaret, who's husband John Baker is a former Conservative councillor, said: "I have thought long and hard about this.

"I have worked closely with Nick Perry, the LibDem parliamentary campaigner, and Cllr Richard Stevens, leader of the Lib Dem Group on Hastings Borough Council, and I have seen their commitment to the Option Five campaign – which will remain cross-party.

"The Lib Dems have backed a two-site solution right down the line, and this has really impressed me."

Nick Perry, 31, the Lib Dem parliamentary candidate for Hastings and Rye, has welcomed Margaret's membership. He said: "I am absolutely delighted that Margaret has decided to join us."

"I have found her inspirational to work alongside in the fight to protect local maternity services. I look forward to working with her closely into the future, as the Liberal Democrats offer a radical alternative to the Labour-Tory consensus that is turning people off politics left, right and centre."

Responding to the news, MP Michael Foster said: "I think that Margaret recognises that I have been 100 per cent in favour of retention of services at the Conquest, and she takes a wider view about that.

"She is a person who's dedicated to improving health services locally, and how she chooses to pursue that is up to her."

Conservative parliamentary candidate Amber Rudd said it was a great loss to the tories. She said: "Margaret Williams stands for a lot of conservative values. She's a local hero.

"But it's not going to change my commitment to work alongside her."