WASHINGTON — Living up to his reputation as a fearsome corporate raider, Carl Icahn struck against Blockbuster Thursday, vowing to nominate his own slate of directors at the company’s upcoming annual meeting and threatening a takeover of the vidtailer if his demands aren’t met.

Icahn — now the largest single Blockbuster shareholder — excoriated management for mishandling the failed acquisition of Hollywood Entertainment in a letter sent to Blockbuster chairman-CEO John Antioco that was disclosed in a Securities and Exchange Commission filing.

Wall Streeters had wondered when Icahn would jump into the Blockbuster fray after keeping a relatively low profile.

His letter took dead aim at Antioco, calling his recently reported pay package of $54 million “unconscionable” and finding fault in “the way you are running the company.”

Icahn also accused the company of going on a “spending spree” in pursuit of dubious new business plans, such as eliminating the traditional late-fee plan and waging an aggressive monthly subscription plan to challenge popular Internet rental company Netflix.

Icahn said he will nominate his slate of independent directors at Blockbuster’s May 11 annual shareholder meeting.

He said his slate would attempt to bring discipline to spending; control any further “egregious” bonuses; strongly urge the board to give greater dividends to shareholders; and make sure that any offers for the company see the “light of day.”

“If we cannot bring about those changes to our satisfaction, we plan to attempt to take control of board of directors in the 2006 annual meeting,” Icahn wrote.

Icahn has been steadily accumulating Blockbuster shares. According to the filing, he now controls 11.4 million Class A shares, or 9.7% of the total, and 5.5 million Class B shares, or 7.7% of the total.

Icahn also accumulated a nearly 11% stake in Hollywood over the course of the long bidding war for the company, and had wanted a Blockbuster-Hollywood merger.

Instead, Movie Gallery won the fierce bidding war for Hollywood.

Icahn said Blockbuster’s decision to drop its bid for Hollywood in the face of resistance from federal regulators was a “grave error.”

In a statement, Blockbuster dismissed Icahn’s criticisms as sour grapes.

“He was heavily invested in our acquisition of Hollywood, which did not go through for reasons outside our control, and now he’s looking for a short term payback,” a company spokesman said.

News of Icahn’s tirade, which broke just before the closing bell on Wall Street, sent shares of Blockbuster soaring in late-day trading. Shares were up 57¢ to close at $9.70, a 6.24% gain.

The move appeared to catch many investors off guard, as they focused on Icahn’s apparent continued interest in Hollywood.

Some Wall Street analysts were puzzled by many of Icahn’s criticisms of Blockbuster in his letter.

“You have to look at the fact that this is a mature business,” McAlpine Associates president Dennis McAlpine said.

“Is Antioco chasing some wild geese? Probably. The trouble is you don’t know yet which ones are the wild geese and which ones are the pheasants. So I don’t know what else you do,” McAlpine said.

The Blockbuster spokesman also took issue with Icahn’s criticism of Antioco’s pay package, noting that the details of the agreement had been previously disclosed at the time of Blockbuster’s split off from Viacom. The spokesman called the recently reported value of the package of $54 million “misleading.”

“The value of the package is contingent on John’s continued employment and on significant future stock appreciation,” the spokesman said. “It was designed to keep John involved in the company over the next five years and focused on increasing shareholder value.”