The Senate has severely scaled back the Stock Act, the law to stop members of Congress and their staff from trading on insider information, in an under-the-radar vote that has been sharply criticised by advocates of political transparency.

The changes, if they become law, will exclude Congressional and White House staff members from having to post details of their shareholdings online. They will also make online filing optional for the president, vice-president, members of Congress and congressional candidates.

The House was expected to pass a similar bill on Friday.