The National Labor Relations Board said on Tuesday that it would require companies to post notices on their bulletin boards — and perhaps send out e-mail– to inform employees of their right to unionize under federal law.

A day earlier, the labor board's acting general counsel said that he would push for stronger action to create a fair atmosphere for unionization drives, perhaps by letting unions post materials on a company's bulletin board if a company was found to have committed serious violations during such a drive.

These moves, part of a series of recent pro-union actions by the labor board under President Obama, upset companies and business groups.

The National Labor Relations Board said on Tuesday that it would require companies to post notices on their bulletin boards — and perhaps send out e-mail– to inform employees of their right to unionize under federal law.

A day earlier, the labor board's acting general counsel said that he would push for stronger action to create a fair atmosphere for unionization drives, perhaps by letting unions post materials on a company's bulletin board if a company was found to have committed serious violations during such a drive.

These moves, part of a series of recent pro-union actions by the labor board under President Obama, upset companies and business groups.