President Obama signed his first piece of legislation before a cheering crowd of women union workers in the White House yesterday: a law giving women the right to equal pay when they do the same job as men.

The star of the event, who stood by Mr Obama as he declared it a “wonderful day”, was Lilly Ledbetter, the Alabama woman after whom the new law was named because of her equal-pay crusade against the Goodyear Tyre company.

Mrs Ledbetter, 70, discovered after 19 years working at a Goodyear plant in Alabama that she had been paid significantly less than men at the factory who did the same job. She found out that she was the lowest-paid superviser there, despite having more qualifications and experience than some of them. She sued, but the US Supreme Court ruled that she had waited too long to bring her lawsuit.

Mrs Ledbetter's case became a cause célèbre, especially after Republicans in Congress - including John McCain, Mr Obama's presidential opponent - blocked efforts by Democrats to pass an equal-pay law.

A lifelong Republican, she even filmed an advertisement for Mr Obama during the White House campaign, decrying Mr McCain's move to stop her getting what she claimed was more than $200,000 (£140,000) in lost salary, and even more in pension benefits. It was one of the most effective commercials of the campaign as it resonated powerfully with women.

After hugging Mrs Ledbetter - whom he and his wife Michelle got to know well on the campaign trail - Mr Obama said: “It is fitting that the very first Bill that I sign, the Lilly Ledbetter Fair Pay Restoration Act, is upholding one of this nation's founding principles: that we are all created equal, and each deserve a chance to pursue our own version of happiness.” Also looking on was Hillary Clinton, Mr Obama's Secretary of State, and Nancy Pelosi, the House Speaker.

Mr Obama said of Mrs Ledbetter: “This grandmother from Alabama kept on fighting, because she was thinking about the next generation.” He added: “I sign this Bill for my daughters, and all those who will come after us, because I want them to grow up in a nation that values their contributions.”

Mrs Obama, in a separate reception with Mrs Ledbetter in the State Dining Room, said: “She knew unfairness when she saw it, and was willing to do something about it because it was the right thing to do - plain and simple.”

Mrs Ledbetter will still not be paid any money by Goodyear, but said: “With the President's signature today, I have an even richer reward.”

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