The influential conservative group Club For Growth has dealt a major blow to House GOP efforts to link infrastructure investment and domestic energy production by urging House members to vote down the bill.

The group called the "American Energy & Infrastructure Act" (H.R. 7) a "remarkably bloated and inefficient piece of legislation," deriding it for adding to the nation's transportation spending. The group says a better bill would have handed authority back to states, while ending or reducing the federal gas tax.

"Simply put, this is a massive 846-page bill that doesn't cut any spending at all," the group said in a statement. "Indeed, it spends at least $30 billion more by supplementing fuel taxes with additional revenue from other sources."

House leaders have been talking up the measure as valuable -- Transportation and Infrastructure Chairman John Mica (R-Fla.) has called it the most important jobs bill this year -- and are quick to brandish its conservative credentials. The bill removes earmarks, consolidates federal bureaucracy, cuts project reviews and reduces some spending Republicans have branded as wasteful.

In a speech to his conference yesterday, Speaker John Boehner (R-Ohio) said the bill, set to be marked up by the T&I Committee today, was "significantly more conservative, and deserving of your support" than previous highway bills.

Still, that is not enough to convince the Club for Growth, who said the talk about changing the transportation system was "standard politician-speak for slowing down the reform agenda so that business-as-usual can resume sometime in the near future when nobody is looking."

Several other conservative groups -- including Taxpayers for Common Sense, the Competitive Enterprise Institute and Heritage Action for America -- have expressed concerns about the bill's use of domestic energy production to pay for its overall spending levels.

And some transportation groups -- notably AAA and the American Public Transportation Association -- are urging members to make changes during today's markup on controversial issues ranging from rules governing truck weight to funding levels for mass transit.

Leaders on the T&I Committee expect today's markup to be a difficult one. Ranking member Nick Rahall (D-W.Va.) said "a lot of things" were controversial and that Democrats are expected to have many objections to the more than 800-page bill, which was not formally released until Tuesday.

Mica said he would not hold back at the markup, saying he was "open to full participation by members."

Reporter Jeremy P. Jacobs contributed.