Mr Eliot Spitzer, New York attorney general, will step up his reform of mutual fund trading over the next two weeks by filing several civil and criminal charges against fund companies.

The purpose of the moves is to create a steady drumbeat of charges that will lead to structural reform of the $7,000 billion US fund management industry. His initial targets, people familiar with the plans say, include the Invesco unit of Amvescap, Strong Capital Management, Alliance Capital Management and Security Trust. Scores of other fund management companies are also under investigation by Mr Spitzer's office and other regulators, including the US Securities and Exchange Commission.

Any accusations will be accompanied by lawsuits from the SEC, the US's chief financial regulator. Its division of enforcement is conducting the investigations in tandem with Mr Spitzer's office. In spite of occasional inflammatory rhetoric, the two regulators are working well together at an enforcement level, people on both sides agree.

The charges expected to be filed by Mr Spitzer's office over the coming weeks, whether criminal or civil, are likely to be connected to failure to stop improper short-term trading, known as market timing, that decreases returns for long-term investors and is discouraged by most fund companies. The practice was pervasive at some of the companies and in some instances was condoned, promoted and committed by senior executives, the people familiar with the matter said.

A spokeswoman for Mr Spitzer declined to comment. The SEC would not comment. At the end of last week discussions were still being held among lawyers.