Shirley Williams, the former Labour cabinet minister who broke away from the party to form the SDP, has died, her current party, the Liberal Democrats, has said. She was 90.

In a statement Lib Dem leader Sir Ed Davey paid tribute to Baroness Williams of Crosby as a “true trailblazer” who had inspired millions.

As a Labour minister, Lady Williams, served in the governments of Harold Wilson and James Callaghan in the 1970s rising to become education secretary.

However in 1981, having become disillusioned with Labour’s drift to the left under Michael Foot, she was one of the original “Gang of Four” to leave the party to form the new centrist SDP.

Sir Ed said that her bravery continued to inspire Liberal Democrats to this day.

“Shirley has been an inspiration to millions, a Liberal lion and a true trailblazer. I feel privileged to have known her, listened to her and worked with her. Like so many others, I will miss her terribly,” he said.

“Political life will be poorer without her intellect, her wisdom and her generosity. Shirley had a limitless empathy only too rare in politics today; she connected with people, cared about their lives and saw politics as a crucial tool to change lives for the better.

“As a young Liberal, Shirley Williams had a profound impact on me, as she did on countless others across the political spectrum. Her vision and bravery, not least in founding the SDP, continues to inspire Liberal Democrats today.”

Lady Williams first entered Parliament as a Labour MP in 1964.

Social Democratic Party launch
Shirley Williams with her fellow ‘Gang of Four’ members (from the left) Roy Jenkins, David Owen and Bill Rodgers (PA)

Originally seen as being on the left of the party, as education secretary in the 1970s she supported the comprehensive system and the abolition of grammar schools.

But by the turbulent years of the early 1980s, alarmed at the direction it was taking under Michael Foot, she joined David Owen, Roy Jenkins and Bill Rodgers in the new SDP in an attempt to “break the mould of British politics”.

The party enjoyed some initial success in alliance with the Liberal Party, with Lady Williams winning Crosby for the SDP in a notable by-election, only to lose it two years later in the 1983 general election.

After the SDP failed to make the electoral breakthrough its founders had hoped for, she became an advocate of merger with the Liberals in what eventually became the current Liberal Democrat Party.

In 1993, she was made a life peer finally retiring as the party’s leader in the House of Lords in 2004.

Boris Johnson paid tribute to Lady Williams, describing her as “a kind and thoughtful member of the once radical centre left”.

“Even when we disagreed – as we often did – she had the gift of sounding so completely reasonable at all times,” he said.

“I spent many happy hours sparring with her on Question Time. She will be much missed.”

Former prime minister Tony Blair said that even after she left Labour, she remained a source of inspiration to many in the party.

“Shirley Williams was one of the greatest social democrats of the last century, an immense figure of progressive politics through the decades, consistent in her commitment to equality, to social justice, to liberal social democratic values and to internationalism,” he said.

“For many of us in the Labour Party and even after she left it, she remained a source of inspiration and someone to look up to and admire – warm, generous, humane, and uplifting. She will be greatly missed.”

Commons Speaker Sir Lindsay Hoyle said she was “one of a kind”.

“She was a trailblazer for women and education, one of the first women to sit in cabinet and the only female member of the ‘Gang of Four’.

“Without doubt, she was one of a kind, and a character we all shall miss.”

Former prime minister Gordon Brown said: “I am very sad to hear of Shirley Williams’ death. I had the privilege of working with her in her efforts to achieve nuclear disarmament and greater co-operation in Europe, causes she steadfastly supported throughout all her political life.

“Her deep commitment to social democratic values will long be remembered.”