K Street’s biggest firms posted strong performances in the first half of 2010, with four of the top five firms reporting double-digit gains and several midsized lobbying shops continuing to show steady growth.

Nineteen of the top 25 firms reported growth in revenue following an erratic 2009.

The lobbying practices’ dramatic numbers come out of a legislative frenzy on Capitol Hill, with K Street focused on health care reform, a financial services regulatory overhaul and climate change legislation. In total, the top 25 firms grossed $227.5 million in the first six months of this year.

The biggest shake-up on the list is among the midsized firms and a handful of relatively younger lobby shops that once again reported double-digit gains.

Brownstein Hyatt Farber Schreck solidified its position among the top-tier firms, breaking into the top five for the first time. While Prime Policy Group, formed late last year from the merger of BKSH & Associates and Timmons & Co., broke into the top 25 after six months in business.

McBee Strategic Consulting, Mehlman Vogel Castagnetti and Breaux Lott Leadership Group also reported double-digit increases for the second year in a row.

The top three lobbying firms — Patton Boggs, Akin Gump Strauss Hauer & Feld and Van Scoyoc Associates — maintained their positions on the list as the top revenue generators. Patton Boggs and Akin Gump both posted double-digit gains over the first half of 2009.

Patton Boggs reported an increase of 12.4 percent, billing clients $20.8 million in the first half of 2010. Kevin O’Neill, deputy chairman of the firm’s public policy practice, said Patton Boggs had an extremely busy first half of the year.

While Patton Boggs completed a merger with Breaux Lott Leadership Group earlier this year, the firms continued to report lobbying revenues separately to the Senate.

Akin Gump Strauss Hauer & Feld had a strong comeback during the first half of this year after dropping about 10 percent in the first half of last year. From January through June, the firm gained 13.1 percent in revenue, billing $18.1 million, according to lobbying reports.

Smith Davis, a partner in Akin Gump’s government relations practice, attributed the growth to a busy legislative calendar and the firm’s merger in March with the all-Democratic lobbying boutique Parven Pomper Strategies. That union brought six lobbyists to the firm as well as Democratic Leadership Council founder Al From, who joined as a consultant.

The biggest change came with Brownstein Hyatt. For the second year in a row, the firm reported about 30 percent growth, blowing past Holland & Knight and Cassidy & Associates, two longtime mainstays as top revenue earners, to round out the top five.

“We’re basically the same size in terms of overhead compared to last year,” Brownstein Hyatt’s Al Mottur said. “I refer to it more as the two R’s — retention and renewal.”

Despite dropping a few rungs, Holland & Knight and Cassidy & Associates each posted revenue gains of $10.8 million for the first six months of the year.

Not all firms were able to maintain a position on the top 25. Carmen Group dropped off the list. The firm, which faced an 8.1 percent drop during the first half of 2009, took another hit during the first half of this year, dropping 7.3 percent to $5.1 million in revenue.

BGR Group and Quinn Gillespie & Associates also continued to struggle in the first half of the year. BGR Group, which faced a drop of 20.6 percent over the same period in 2009, saw its revenue drop an additional 13.6 percent this year to $7 million.

BGR Group’s Loren Monroe acknowledged that the firm’s lobbying numbers were “flat” so far this year. However, he was optimistic about the future noting the hire of Jeff Birnbaum.

“We turned the corner at the start of 2010 with over 30 new clients in the first two quarters retaining BGR’s lobbyists,” Monroe wrote in an e-mail. “We foresee strong growth in the months ahead.”

Most K Streeters, however, were hesitant about whether their firms will continue to show strong growth.

“I’d love it if it were as busy, but a fair answer is we expect some bumps,” Brownstein Hyatt’s Mottur said. “The elections are going to have an impact on the Congress’ ability to act in a lame duck. And assuming predictions are correct about Republican gains in the Senate, for example, the minority will be emboldened to block each and every thing that it thinks it can act on differently in the next Congress with their increasing numbers.”