Serious efforts were needed to advance equality of opportunity in the United States, as the growing inequality endangered the nation's political and economic system, a renowned U.S. economist said Monday.

There was no question that income was distributed substantially more unequally than it was a generation ago in the United States, former U.S. Treasury Secretary Lawrence Summers said in an article carried on the Washington Post.

Those at the top income bracket were gaining share in the social wealth distribution, while those with fewer skills, especially men who in an earlier era would have worked with their hands, were losing ground in absolute and relative terms, warned the former Harvard University president.

"These issues frame an important part of the economic debate in this election year. Progressives argue that widening inequality jeopardizes the legitimacy of our political and economic system," added Summers, who also served as the economic adviser to U.S. President Barack Obama until November 2010.

While progressives argued that a time when the market was generating more inequality was no time to shift tax burdens from those with the highest incomes to the middle class, Summers believed that the most important step that could be taken to enhance equality of opportunity was strengthening public education, in addition to fair tax policies.

"For the past decade we have focused on ensuring that no child is left behind. This effort must continue, but if everyone is to have a real chance for great success we must also ensure that every child in public school can learn as much and go as far as his or her talent permits," Summers added.