Veteran Labour MP Gwyneth Dunwoody, the longest-serving female MP in Parliament, has died at the age of 77.
Mrs Dunwoody, MP for Crewe and Nantwich since 1974, had been ill for the past week, her son said.
Prime Minister Gordon Brown described her as 'politics at its best' and said she would be sadly missed.
As well as chairing the transport select committee, Ms Dunwoody was known as a prominent and much-admired fighter for backbenchers' rights.
Leading the tributes, the prime minister said: "So many people will be so sad to hear of the death of Gwyneth Dunwoody. She was always her own person. She was fiercely independent."
Ms Dunwoody's son David described her as a wonderful mother and grandmother.
He told the BBC she had died 'in a gentle and calm way' on Thursday evening after being ill for about a week.
He said: "She was a woman who stood up and said what she believed was true. She defended people who didn't have anyone else to defend them. Everybody who knew her knew she believed passionately in everything that she did."
Ms Dunwoody joined the Labour Party in 1946 and first entered Parliament as the MP for Exeter in 1966.
Always an independent figure, Mrs Dunwoody was frequently a thorn in the Government's side. In 2001 she survived an attempt by Labour whips to remove her from the transport select committee - which under her chairmanship often produced highly critical reports.
Backbench Labour MPs refused to support the move when it went to a vote in the Commons.
She was also widely admired by transport industry leaders, many of whom were grilled by her over the years at committee hearings.