WASHINGTON (Reuters) - Senator Al Franken, a critic of Comcast Corp's proposed deal for control of NBC Universal, asked the Justice Department on Monday to investigate whether the giant cable company had engaged in "illegal collaboration" concerning its intended target.

Franken said that on September 26 Comcast had named its chief operating officer, Steve Burke, as the prospective chief executive of NBC Universal. Last week, Comcast named several executives who would hold top jobs at NBC Universal after the cable company took control of the broadcaster and movie studio from General Electric Co.

"By announcing the future leadership of NBC Universal well in advance of federal approval, Comcast may be seeking to indirectly exert managerial and operational control of that company," wrote Franken, once a performer on NBC's Saturday Night Live.

But Comcast said transition and integration planning is common, proper, and expected.

"Post-closing management teams are regularly announced prior to antitrust approval. NBC Universal has remained in total control of all decision making to date," said Comcast spokeswoman Sena Fitzmaurice.

An antitrust expert agreed it was not unusual for executives to be named for posts before the companies get government approval to close.

Comcast revealed its bid to buy a controlling stake in NBC Universal from General Electric on December 3, 2009, a $30 billion deal to create a business including broadcast, cable networks, movie studios and theme parks.

Talks between Comcast's representatives and U.S. regulators have intensified in recent days, according to sources, as the company tries to complete the deal by year-end.

Regulators are "likely to impose significant conditions" on the new business, a source told Reuters earlier this month.

(Reporting by Diane Bartz; Editing by Gerald E. McCormick and Tim Dobbyn)