April 5 (Reuters) - Joe Wayland, a senior official in the Justice Department's Antitrust Division who led the agency's first successful court challenge to a merger in 10 years, will take over as acting assistant attorney general for the division, the department said on Thursday.

Wayland, who led the team that sued H&R Block Inc over its acquisition of TaxAct last year, takes over from the previous acting head, Sharis Pozen.

A federal judge in November upheld the Justice Department's challenge to the H&R Block deal, which regulators had alleged reduced competition in the market for do-it-yourself tax preparation products.

Wayland's appointment comes as Congress has not yet acted on a permanent director for the division.

In February the Obama administration nominated William Baer, a former top official at the Federal Trade Commission who is now in private practice, to lead the division.

The current acting director, Sharis Pozen, earlier announced she would step down on April 30.

The Justice Department recruited Wayland in September of 2010 to lead litigation efforts at the division, a hire that appears to have paid off.

In addition to the H&R Block deal, Wayland also helped the department oppose AT&T Inc's proposed merger with Deutsche Telekom's T-Mobile USA Inc, which the companies dropped in December. Regulators had argued that the $39 billion deal would reduce competition in the wireless communications market.

"Joe's leadership and litigation expertise has made him a significant asset to the Antitrust Division and to the department," Attorney General Eric Holder said in a statement.

"I know that he will maintain strong antitrust enforcement during this time of transition," he added.

The division has been without a confirmed head since last July, when Christine Varney left for private practice.

(Reporting By Aruna Viswanatha)

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