Conservative groups are rallying to prevent Congress from taking up any legislation to fund the government during the lame-duck session after the election, and warn that doing so would empower lobbyists over taxpayers.

Free-market groups will put pressure on Congress not to pass a short-term funding bill in September that would require Congress to act again during the lame duck between November and January or else face the threat of a partial government shutdown, said Andy Koenig, senior policy advisor for Freedom Partners.

"If you're a lobbyist who wants anything, you want to sequence in so you're dealing with a spending bill in a must-pass way right before Christmas, dealing with a bunch of members who aren't going to be there any more," explained Koenig.

Freedom Partners, a political nonprofit linked to the Koch brothers that backs fiscally conservative organizations and causes, was one of the groups on a call with reporters Tuesday laying out plans to advocate against a lame-duck spending bill.

Luke Hilgemann, CEO of Americans for Prosperity, said on the call that if members of Congress aimed for a lame-duck spending bill, "We are going to be there to hold them accountable."

The government is funded through September, but beyond then it remains an open question how Congress will fund it.

In recent years, similar must-pass legislation has brought the government close to a partial shutdown, a prospect that was averted last year when then-House Speaker John Boehner passed a budget agreement with Democratic votes and then resigned from office.

Noting that at least 44 members of Congress will be gone after this year and won't have to face voters again after November, Koenig warned of the risks of a lame-duck bill.

"When you have a bunch of members in powerful positions who are leaving, lots of them probably heading to K Street on the way, wheeling and dealing for special favors and goodies in an appropriations, the result is going to be bad for the American taxpayers," Koenig said.

Of particular concern to the right-leaning groups is that the lame-duck Congress could insert measures opposed by conservatives into must-pass legislation. Among the items they are watching out for are bills clearing the path for the Export-Import Bank to resume making large deals or renewing green energy tax breaks.

On Tuesday, the groups released a letter signed by a wide range of right-leaning nonprofits opposing a lame-duck spending bill, and announced their intent to mobilize their memberships to call members of Congress about the issue.

And other conservative organizations weighed in separately.

"As Congress begins work on a continuing resolution, lawmakers must ensure the length of the funding measure does not necessitate a post-election session of Congress," Heritage Action spokesman Dan Holler said in a statement. "It is unfair to the American people to allow unaccountable politicians to make consequential decisions in a lame-duck session."