The focus for opponents of a controversial Internet sales tax is shifting to the House of Representatives, where bipartisan opposition is beginning to build.

The U.S. Senate debated the tax this week, but a final vote is not expected until it returns from recess in early May.

Rep. Annie Kuster, D-N.H., on Thursday reiterated her opposition to the tax legislation and urged Speaker of the House John Boehner to oppose the legislation.

The Marketplace Fairness act has already cleared two procedural votes in the Senate by fillibuster-proof majorities. It would require businesses with more than $1 million in annual revenue from online sales to collect sales taxes on transactions that originate from sales-tax states.

If the bill becomes law, New Hampshire residents would not have to pay sales taxes on their Internet transactions, since the state is one of five without a sales tax . But New Hampshire merchants who sell more than $1 million a year in online goods or services would have to collect the tax on transactions originating from states, counties or cities with sales taxes.

In a letter to Boehner on Thursday, Kuster said that the act would impose overly-burdensome tax collection requirements on New Hampshire's small businesses.

"Before the House of Representatives acts on this proposal, I urge you to consider the adverse impact it would have on the online entrepreneurs who are innovating, creating jobs, driving economic growth and expanding opportunity for the American people," Kuster wrote.

"Instead of needlessly saddling these firms with onerous rules and paperwork, I am hopeful Congress will heed the voices of small online businesses and work in a bipartisan fashion to foster the conditions they need to succeed."